NOVEL SUBSTITUTED FLAVAN DERIVATIVES AND PROCESS FOR THE PREPARATION THEREOF FIELD OF THE INVENTION The present invention relates to novel substituted flavan derivatives of the Formula (I) Formula (I) The present invention also relates to a process for the preparation of phthalonitrile or cyanate ester flavan derivatives. The present invention also relates to use of novel substituted flavan derivatives to produce polymer composite materials. BACKGROUND OF THE INVENTION Polymer matrix composite materials are widely used in a variety of technical fields, such as in the aerospace, automotive, marine, infrastructure, military, sports, and industrial fields. These lightweight materials exhibit excellent mechanical properties, high corrosion resistance, dimensional stability, and low assembly costs. The areas of applications of polymer matrix composites using carbon, glass or quartz fibres are increasing and efforts are being made to use polymer matrix composites in more and more critical applications. One of the factors limiting the use of these materials is the maximum use temperatures which is generally less than 250 C. Phthalonitrile polymers or resins and their composites are considered as the material of choice for high performance applications due to their excellent thermal stability and mechanical properties, elevated glass transition temperatures, high chemical resistance and non- inflammability characteristics. Phthalonitrile resin matrix composites are known to retain a very high percentage (~80%) of their room temperature mechanical, electrical, and dielectric properties at temperatures of 300 to 350 C and are thus excellent candidate materials for aero engine components, missile and launch vehicle structures, submarine and aircraft interiors. A number of different phthalonitrile resins have been described in literature. These resins are generally prepared by end capping bis phenols with phthalonitrile moieties. For examples resins have been prepared from bis phenol A, dihydroxy biphenyl, resorcinol etc. Dhanya et al., RSC Adv. 2016, 5, 91254–91261 discloses a synthesis of phthalonitrile resin bearing cyanate ester group. The sresins bearing both cyanate and phthalonitrile groups in different proportions in the same backbone were synthesized and characterized as follows: EP 3211023 B1 discloses phthalonitrile monomer modified with organosilicon fragments which is characterized by the general formula where X is a bivalent aromatic radical selected from the group consisting of:, wherein R ₃ is a radical selected from the group including CH ₂ , C(CH ₃ ) ₂ , C(CF ₃ ) ₂ , and SO2, and Y is an organosilicon fragment selected from the group consisting of SiR1R2 and SiR1R2-O-SiR1R2 , wherein R1 and R2 are radicals selected from the group consisting of CH ₃ , C ₆ H ₅ , and HC=CH ₂ . The synthesis compounds of general formula disclosed in thus patent is as given below: where, X and Y are as defined above. Journal of Polymer Sci. Part A- Polymer Chem. 2010, 48(20), 4547 – 4554 discloses 1,3,5-tris(1-(4-cyanatophenyl)ethyl)benzene using 1,3,5-tris(1-(4- hydroxyphenyl)ethyl)benzene. The synthetic procedure disclosed in this journal for the preparation of monomer is as given below: US 5,965,268 A discloses a method of making a carbon-based composite material by using phthalonitrile resins as precursors, wherein the phthalonitrile thermoset polymer precursor is a phthalonitrile monomer and a curing agent. The phthalonitrile monomer is a compound of the formula: wherein A is any divalent organic radical. US 2003/0229198 Al discloses a process for the preparation of phthalonitrile monomer comprising the formula: wherein Ar is an independently selected divalent aromatic radical; and wherein n is an even integer greater than or equal to 2; comprising the step of reacting a 3- or 4- nitrophthalonitrile with a hydroxy-terminated aromatic ether oligomer. As can be seen from the above, none of the prior art discloses the phthalonitrile or cyanate ester flavan derivatives. The existing products can be used upto the maximum of temperature 350 °C. In view of the importance, there is a need for developing the compounds to explore extending the maximum use temperature. In this direction, the inventors of the present invention have investigated the influence of phthalonitrile on flavan group for extending the maximum use temperature beyond 400 °C by synthesizing new phthalonitrile flavan resin based on compounds having more than two phenolic hydroxyl groups which involves use of inexpensive raw material which are easily available or prepared from commercially available sources easily and simple synthetic procedure. Further the melt viscosity of conventional phthalonitrile resins is very low in range 50 to 400 mPaS. The low melt viscosity of these resins creates problems in the fabrication of composites. Particularly it is very difficult to make controlled flow prepregs and zero bleed prepregs using these resins. It is also difficult to control the resin bleeding in compression moulding due to the low viscosity of the resin. There is thus a need for phthalonitrile resins which have high viscosity at the processing temperature for applications like compression moulding and preparation of controlled flow prepregs. The current invention relates to preparation of novel phthalonitrile resins which are amorphous solids with a glass transition temperature of 60 to 85 C. When heated to 120 C, the resins become high viscosity liquids with a viscosity of ~ 50000 mPaS. The viscosity will decrease to about 10000 to 20000 mPaS at 180 C which is the curing temperature of the resin. The novel phthalonitrile resins are prepared from trihydroxy flavan structures. The trihydoxy flavans are prepared by condensation of ketones with resorcinol. The ketones that can used include acetone, cyclopentanone, cyclohexanone, methyl ethyl ketone etc. The flavans have a unique cycloaliphatic bridge between the aromatic rings of resorcinol. The cycloaliphatic bridge provides a semi flexible link providing increased toughness to the cured resin without reducing the high temperature capabilities. Additionally the phthalonitrile resins of this invention have excellent film forming characteristics. Controlled flow or zero bleed prepregs can be very easily manufactured by hot melt film transfer process using the phthalonitrile resins of this invention. Further, unlike the conventional phthalonitrile resins, the resins of this invention do not need to be converted into prepolymers for the manufacture of prepregs. The monomeric resin itself can be used along with a curing agent without the addition of any other modifiers greatly simplifying the process of making prepregs. The phthalonitrile resins of this invention can be cured in the same manner as conventional phthalonitriles. They can be cured using aromatic diamines, phthalonitriles of amino phenols etc., as a curing agent agents at temperature of 180 to 200°C. The cured resin can be further post cured at 350 to 400°C to enhance the thermal stability of the cured resins. The post cured resins will have glass transition temperature >400°C and decomposition temperature > 475°C. Additionally, cyanate esters are addition curable resins. The -OCN groups in cyanate and -CN groups in phthalonitrile have similar mechanism of curing; it was of interest to investigate the cure behaviour of a resin possessing both the groups on the flavan based structure. The present invention was also to carry out the preparation of cyanate ester (–OCN) and phthalonitrile groups linked on to the same positions and to examine the implications of these structural modifications on cure behaviour and thermal properties of the resultant resins. For this, cyanate ester monomers were prepared with free phenolic functional groups that gives provision for further chemical modifications if required i.e free phenolic groups to phthalonitrile groups. OBJECTIVE OF THE INVENTION The main objective of the present invention is to provide novel substituted flavan derivatives Formula (I). Formula (I) wherein, R is nitrile, nitrile substituted benzene which is further optionally substituted; and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from hydrogen, linear or branched C ₁ -C ₁₀ alkyl; R ₂ and R ₃ or R ₄ and R ₅ may be taken together with the carbon atom to which they are attached form an optionally substituted 3-7 membered ring containing 0-3 hetero atoms or groups independently selected from N, O, NH and CO. Another objective of the present invention is to provide a process for the preparation of phthalonitrile or cyanate ester flavan derivatives. Still another objective of the present invention is to provide the use of flavan derivatives to produce polymer composite materials which can be used in a variety of technical fields, such as in aerospace, automotive, marine, infrastructure, military, sports, and industrial fields. SUMMARY OF THE INVENTION Accordingly, the present invention relates to novel substituted flavan derivatives Formula (I). Formula (I) wherein, R is nitrile, nitrile substituted benzene which is further optionally substituted; and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are independently selected from hydrogen, linear or branched C ₁ -C ₁₀ alkyl; R ₂ and R ₃ or R ₄ and R ₅ may be taken together with the carbon atom to which they are attached form an optionally substituted 3-7 membered ring containing 0-3 hetero atoms or groups independently selected from N, O, NH and CO. In another aspect, the present invention provides novel phthalonitrile flavan type compound of Formula (Ia). Formula (Ia) In another aspect, the present invention provides novel phthalonitrile flavan type compound of Formula (Ib). Formula (Ib) In another aspect, the present invention provides novel phthalonitrile flavan type compound of Formula (Ic). Formula (Ic) In another aspect, the present invention provides novel cyanate ester flavan derivative of Formula (Id). Formula (Id) In another aspect, the present invention provides a process for the preparation of novel substituted flavan derivatives of Formula (I). Formula (I) wherein, R is nitrile, nitrile substituted benzene which is further optionally substituted; R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are as defined above; wherein the process comprises reaction of compound of Formula (II) Formula (II) wherein, R ₁ , R ₂ , R ₃ , R ₄ ,R ₅ and R ₆ are as defined above; with nitrobenzene dinitrile or halonitrile using a base in presence of suitable solvent to give compound of Formula (I). In another aspect, the present invention provides a process for the preparation of novel substituted flavan derivatives. In still another aspect, the present invention provides the use of flavan derivatives of Formula (I) Formula (I) wherein, R is nitrile groups, substituted or unsubstituted benzene wherein the substitutions are nitrile groups; and R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are as defined above; to produce polymer composite materials which can be used in a variety of technical fields, such as in aerospace, automotive, marine, infrastructure, military, sports, and industrial fields. BRIEF DESCRIPTION OF THE DRAWINGS The above objectives, aspects, and advantages of the subject matter of present invention is further described by following drawings, where: Figure 1: FR-IR spectra of compound of Formula (Ia) Figure 2: Proton NMR spectrum of compound of Formula (Ia) Figure 3: Carbon NMR spectrum of compound of Formula (Ia) Figure 4: Mass spectrum of compound of Formula (Ia) Figure 5: DSC spectrum of compound of Formula (Ia) Figure 6: FR-IR spectra of compound of Formula (Ic) Figure 7: Proton NMR spectrum of compound of Formula (Ic) Figure 8: Mass spectrum of compound of Formula (Ic) Figure 9: DSC spectrum of compound of Formula (Ic) DETAILED DESCRIPTION OF THE INVENTION The group “R” as used herein and is not limited to nitrile, nitrile substituted benzene which is further optionally substituted, specifically phthalonitrile. The substitutions on benzene group as used herein are not limited to nitrile groups. The group “R” as used herein is specifically nitrile, phthalonitrile groups. The “alkyl” group as used herein is same or different and independently represent unsubstituted or substituted groups selected from C ₁ -C ₁₀ alkyl such as methyl, ethyl, n-propyl and the like; the substituents include hydroxy, halogen such as fluorine, chlorine, bromine and the like; nitro, cyano or amino, (C ₁ -C ₆ ) alkyl, (C ₁ -C ₆ ) alkoxy, aryl or aroyl groups. Substituents as used herein is selected from hydroxy, halogen such as fluorine, chlorine, bromine and the like; nitro, cyano or amino, (C ₁ -C ₆ ) alkyl, (C ₁ -C ₆ ) alkoxy, aryl or aroyl groups. In one particular embodiment, the present invention specifically provides compounds of Formula (I) selected from the group consisting of: phthalonitrile derivative of 2,4,4-trimethyl-7,2’,4’-trihydroxyflavan (Compound of Formula (Ia)); phthalonitrile derivative of 2',4',7-trihydroxy-2,3-propanoflavan-4- spirocyclopentane (Compound of Formula (Ib)); phthalonitrile derivative of 2,3-butano-2',4',7-trihydroxyflavan-4- spirocyclohexane (Compound of Formula (Ic)); and 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)). In another particular embodiment, the definition of “substituted flavan derivatives of Formula (I)” inherently includes all stereoisomers of the compound of Formula (I) either as pure stereoisomer or as a mixture of two or more stereomers. The word stereoisomers includes enantiomers, diasteroisomers, racemates, cis isomers, trans isomers and mixture thereof. In another particular embodiment, the definition of “substituted flavan derivatives of Formula (I)” inherently includes absolute configuration at an asymmetric atom is specified by either R or S. Resolved compounds whose absolute configuration is not known can be designated by (+) or (-) depending on the direction in which they rotate plane polarized light. When a specific stereisomer is identified, this means that said stereoisomer is substantially free, i.e. associated with less than 50%, preferably less than 20%, more preferably less than 5%, in particularly less than 2% or 1% of the other isomers. Thus when a compounds of formula (I) is for instance specified as (R), this means that the compound is substantially free of (S) isomer; when the compound of Formula (I) is for instance specified as E, this mens that the compound is free of the Z isomer; when the compounds of Formula (I) is for instance specified as cis isomer, this means that the compound is free of the trans isomer. In another embodiment, the present invention also provides a process for the preparation of phthalonitrile flavan derivative of Formula (Ia)

Formula (Ia) wherein the process comprising reaction of compound of Formula (IIa) Formula (IIa) with compound of Formula (III) Formula (III) using a base in presence of suitable solvent to give compound of Formula (Ia). In another embodiment, the present invention also provides a process for the preparation of phthalonitrile flavan derivative of Formula (Ib) Formula (Ib) wherein the process comprising reaction of compound of Formula (IIb) Formula (IIb) with compound of Formula (III) Formula (III) using a base in presence of suitable solvent to give compound of Formula (Ib). In another embodiment, the present invention also provides a process for the preparation of phthalonitrile flavan derivative of Formula (Ic) Formula (Ic) wherein the process comprising reaction of compound of Formula (IIc) Formula (IIc) with compound of Formula (III) Formula (III) using a base in presence of suitable solvent to give compound of Formula (Ic). In yet another embodiment, the present invention provides a process for the preparation of cyanate ester flavan derivative of Formula (Id) Formula (Id) wherein the process comprising reaction of compound of Formula (IIa) Formula (IIa) with halonitrile using a base in presence of suitable solvent to give compound of Formula (Id). In yet another preferred embodiment, the present invention provides a simple, economical and commercially feasible procedure for synthesis of phthalonitrile or cyanate ester flavan derivatives with commercially acceptable high temperature capabilities. In yet another preferred embodiment, the present invention provides use of flavan derivatives to produce polymer composite materials which can be used in a variety of technical fields, such as in aerospace, automotive, marine, infrastructure, military, sports, and industrial fields. The reactions of the present invention are carried out in the absence or presence of a solvent. The volumes of the solvents as used herein as taken appropriately based on the quantities of the reactants and reagents. Any of the above reaction steps referred herein is carried out at a temperature in the range -10 °C to 60 °C. The reaction of phthalonitrilation as given in the present invention is carried out at a temperature in the range 30 °C to 40 °C. The nitrilation reaction as given in the present invention is carried out at a temperature in the range -10 °C to 40 °C. The purification as given in any of the reaction steps referred herein is carried out at a temperature in the range -10 °C to 60 °C. In yet another embodiment, solvent used in the present invention is selected from water or "alcohol solvents" such as methanol, ethanol, n-propanol, isopropanol, n-butanol and t-butanol and the like or "hydrocarbon solvents" such as benzene, toluene, xylene, heptane, hexane and cyclohexane and the like or "ketone solvents" such as acetone, ethyl methyl ketone, diethyl ketone, methyl tert-butyl ketone, isopropyl ketone and the like or "esters solvents" such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, and the like or "nitrile solvents" such as acetonitrile, propionitrile, butyronitrile and isobutyronitrile and the like or "ether solvents" such as di-tert-butylether, dimethylether, diethylether, diisopropyl ether, 1,4-dioxane, methyltert-butylether, ethyl tert-butyl ether, tetrahydrofuran, 2-methyl tetrahydrofuran, 2-methoxyethanol and dimethoxyethane, or “Amide solvents” such as formamide, DMF, DMAC, N- methyl-2-pyrrolidone, N-methylformamide, 2-pyrrolidone, 1-ethenyl-2-pyrrolidone, haloalkanes such as dichloromethane, 1,2-dichloroethane and chloroform, “Amine solvents” selected from diethylenetriamine, ethylenediamine, morpholine, piperidine, pyridine, quinoline, tributylamine, diisopropyl amine and/or mixtures thereof. In yet another preferred embodiment, base used in the present invention is selected from either inorganic base like alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and lithium carbonate; Alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal alkoxides such as sodium methoxide, potassium methoxide, sodium tertiary butoxide, potassium tertiary butoxide or mixtures thereof; alkyl metals such as n-butyl lithium or silicon-based amides, such as sodium and potassium bis(trimethylsilyl)amide, Lithium hexamethyldisilazide, Sodium hexamethyldisilazide and potassium hexamethyldisilazide or organic bases such as LDA (lithium diisopropylamide), triethylamine, triethanolaminetributylamine, N-methylmorpholine, N,N-diisopropylethylamine, di-n-propylamine, N-methylpyrrolidine, pyridine, 4-(N,N- dimethylamino)pyridine, morpholine, imidazole, 2-methylimidazole, 4- methylimidazole, 1,4-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5- ene (DBN), 1,4-diazabicyclo[2.2.2]-octane (DABCO) and the like. The synthesized phthalonitrile or cyanate ester flavan derivatives of Formula (1a) and Formula (1b) were characterized using FT-IR spectroscopy. The curing study of synthesized compounds were studied by Differential Scanning Calorimetry (DSC). The thermal stability of was analyzed using Thermo gravimetric Analyzer (TGA). The current invention relates to preparation of novel phthalonitrile resins which are amorphous solids with a glass transition temperature of 60 to 85 C . When heated to 120 C the resins become high viscosity liquids with a viscosity of ~ 50000 mPaS. The viscosity will decrease to about 10000 to 20000 mPaS at 180 C which is the curing temperature of the resin. The novel phthalonitrile resins are prepared from tri hydroxy flavan structures. The trihydoxy flavans are prepared by condensation of ketones with resorcinol. The ketones that can used include acetone, cyclopentanone, cyclohexanone, methyl ethyl ketone etc. The resins are particularly suitable for production of zero bleed prepregs with carbon fibres, glass fibres or quartz fibres. The prepregs can be used for the manufacture composite components for aeroengine components, structural components of missiles, airframe, launch vehicles and satellites which are required to function at high temperatures in the range 250°C to 350°C. The resins can also be used for preparation of compression moulding compounds. The flavans have a unique cycloaliphatic bridge between the aromatic rings of resorcinol. The cycloaliphatic bridge provides a semi flexible link providing increased toughness to the cured resin without reducing the high temperature capabilities. Additionally the phthalonitrile resins of this invention have excellent film forming characteristics. Controlled flow or zero bleed prepregs can be very easily manufactured by hot melt film transfer process using the phthalonitrile resins of this invention. Further, unlike the conventional phthalonitrile resins, the resins of this invention do not need to be converted into prepolymers for the manufacture of prepregs. The monomeric resin itself can used along with a curing agent without the addition of any other modifiers greatly simplifying the process of making prepregs. The phtalonitrile resins of this invention can be cured in the same manner as conventional phthalonitriles. They can be cured using aromatic diamines, phthalonitriles of amino phenols etc. Additionally, cyanate esters are addition curable resins. The -OCN groups in cyanate and -CN groups in phthalonitrile havie similar mechanism of curing; it was of interest to investigate the cure behaviour of a resin possessing both the groups on the flavan based structure. The present invention was also to evaluate the preparation of cyanate ester (–OCN) and phthalonitrile groups linked on to the same positions and to examine the implications of these structural modifications on cure behaviour and thermal properties of the resultant resins. For this, Cyanate ester monomers were prepared with free phenolic functional groups that give provision for further chemical modifications is required i.e cyanate ester to phthalonitrile groups. The present invention is further illustrated by the following examples which are provided merely to be exemplary of the inventions and is not intended to limit the scope of the invention. Certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention. EXAMPLES Example-1: Synthesis of 2,4,4-trimethyl-7,2’,4’-trihydroxyflavan (Compound of Formula (IIa): Resorcinol (110 g, 1.0 mol), acetone (58 g, 1.0 mol) and distilled water (200 ml) were taken in a double necked round bottom flask and stirred for few minutes to get clear solution. To this mixture, 37 % HCl solution (16.5 ml) was added drop wise using dropping funnel at room temperature and the resulting mixture was stirred for 48 hours at room temperature. The obtained solid product was filtered under vacuum. Dry the wet material to get title compound as a white solid (87 g, 79% yield) Example-2: Synthesis of phthalonitrile derivative of 2,4,4-trimethyl-7,2’,4’- trihydroxyflavan (Compound of Formula (Ia)): 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), 4-nitrophthalonitrile (52.5 g, 0.3mol) were dissolved in DMSO (300 ml) in a round bottom flask. Potassium carbonate (41.6g, 0.3mol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction (monitored by TLC), reaction mass was poured slowly into water (750ml). The obtained solid product was filtered and dried to get the title compound (49.7 g, 73% yield). Example-3: Synthesis of phthalonitrile derivative of 2,4,4-trimethyl-7,2’,4’- trihydroxyflavan (Compound of Formula (Ia)): 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), 4-nitro phthalonitrile (52.5 g, 0.3mol) were dissolved in DMF (250 ml) in a round bottom flask. Potassium carbonate (41.6g, 0.3mol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction (monitored by TLC), reaction mass was poured slowly into water (750ml). The obtained solid product was filtered and dried to get the title compound (48.7 g, 71.5% yield). Example-4: Synthesis of phthalonitrile derivative of 2,4,4-trimethyl-7,2’,4’- trihydroxyflavan (Compound of Formula (Ia)): 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), 4-nitro phthalonitrile (52.5 g, 0.3mol) were dissolved in NMP (300 ml) in a round bottom flask. Potassium carbonate (41.6g, 0.3mol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction (monitored by TLC), reaction mass was poured slowly into water (750ml). The obtained solid product was filtered and dried to get the title compound (57.8 g, 85.2% yield). Example-5: Synthesis of phthalonitrile derivative of 2,4,4-trimethyl-7,2’,4’- trihydroxyflavan (Compound of Formula (Ia)): 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), 4-nitrophthalonitrile (52.5 g, 0.3mol) were dissolved in DMSO (300 ml) in a round bottom flask. Sodium hydroxide (12 g, 0.3mol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction (monitored by TLC), reaction mass was poured slowly into water (750ml). The obtained solid product was filtered and dried to get the title compound (43.2 g, 63.5% yield). Example-6: Synthesis of 2' ,4' ,7-trihydroxy-2,3-propanoflavan-4-spirocyclo pentane (Compound of Formula (IIb)): Resorcinol (39.65 g, 360mmol), cyclopentanone (10.11 g, 120mmol) and distilled water (400 ml) taken in a four necked round bottom flask and stirred for few minutes to get clear solution. To this solution, 37 % HCl solution (15 ml) was added drop wise at room temperature and the resulting mixture was stirred for 48 hours at room temperature. After completion of the reaction, product was extracted with dichloromethane solvent (3 x 100 ml) from reaction mixture. Organic layer was washed with water (3 x 50 ml), and dried over anhydrous sodium sulphate. Organic layer was concentrated under reduced pressure to obtain 14 g of viscous substance. Example-7: Synthesis of phthalonitrile derivative of 2' ,4' ,7-trihydroxy-2,3- propanoflavan-4-spirocyclo pentane (Compound of Formula (Ib)): 2' ,4' ,7-Trihydroxy-2,3-propanoflavan-4-spirocyclopentane (4g, 11.35mmol), 4-nitro phthalonitrile (5.9 g, 34mmol) were dissolved in DMSO (30 ml) in round bottom flask. Potassium carbonate (4.7g, 34mmol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction, reaction mass was poured into water (250ml) while stirring. The product was extracted with dichloromethane (3 x 50ml) from aqueous layer. Organic layer was washed with water (3 x 25ml), dried over anhydrous Na ₂ SO ₄ and concentrated under reduced pressure to get 6g of title product. Example-8: Synthesis of phthalonitrile derivative of 2' ,4' ,7-trihydroxy-2,3- propanoflavan-4-spirocyclo pentane (Compound of Formula (Ib)): 2' ,4' ,7-Trihydroxy-2,3-propanoflavan-4-spirocyclopentane (4g, 11.35mmol), 4-nitro phthalonitrile (5.9 g, 34mmol) were dissolved in DMF (30 ml) in round bottom flask. Potassium carbonate (4.7g, 34mmol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction, reaction mass was poured into water (250ml) while stirring. The product was extracted with dichloromethane (3 x 50ml) from aqueous layer. Organic layer was washed with water (3 x 25ml), dried over anhydrous Na ₂ SO ₄ and concentrated under reduced pressure to get 5.5 g of title product. Example-9: Alternative process for the synthesis of phthalonitrile derivative of 2' ,4' ,7-trihydroxy-2,3-propanoflavan-4-spirocyclopentane(Compound of Formula (Ib)): 2' ,4' ,7-Trihydroxy-2,3-propanoflavan-4-spirocyclopentane (4g, 11.35mmol), 4-nitro phthalonitrile (5.9 g, 34mmol) were dissolved in DMSO (30 ml) in round bottom flask, sodium hydroxide (0.14 g, 34mmol) was added in four lots to the above mixture and stirred for 24 hours at room temperature. After completion of the reaction, reaction mass was poured into water (250ml) while stirring. The product was extracted with dichloromethane (3 x 50ml) from aqueous layer. Organic layer was washed with water (3 x 25ml), dried over anhydrous Na ₂ SO ₄ and concentrated under reduced pressure to get 5.5 g of title product. Example-10: Synthesis of 2,3-Butano-2' ,4' ,7-trihydroxyflavan-4-spirocyclohexane (Compound of Formula (IIc)): Resorcinol (20.85 g, 189.37mmol), cyclohexanone (6 g, 61.13mmol) and distilled water (200ml) were taken in a double necked round bottom flask and stirred for few minutes to get clear solution. To this mixture, 37 % HCl solution (7.8 ml) was added drop wise and the mixture was stirred for 48 hours at room temperature. After completion of the reaction, filter the product. Obtained product was made into slurry by adding 50ml distilled water. Filtered and dry the solid to get title compound (9 g) Example-11: Synthesis of phthalonitrile derivative of 2, 3- butano-2' , 4' , 7- trihydroxy flavan -4-spirocyclo hexane (Compound of Formula (Ic)): 2,3-Butano-2' ,4' ,7-trihydroxyflavan-4-spirocyclohexane (4g, 10.51mmol), 4- nitrophthalonitrile (5.46 g, 31.53mmol) were dissolved in DMSO solvent (30ml) in a round bottom flask. Potassium carbonate (4.56 g, 32.99mmol) was added in four lots to above mixture and stirred at room temperature for 24 hours. After completion of the reaction, pour the reaction mass into water (250ml) while stirring. Filtered the product and dried to get the title compound (6.5 g). Example-12: Synthesis of phthalonitrile derivative of 2, 3- butano-2' ,4' ,7- trihydroxy flavan-4-spirocyclo hexane (Compound of Formula (Ic)): 2,3-Butano-2' ,4' ,7-trihydroxyflavan-4-spirocyclohexane (4g, 10.51mmol), 4- nitrophthalonitrile (5.46 g, 31.53mmol) were dissolved in DMF solvent (30ml) in a round bottom flask. Potassium carbonate (4.56 g, 32.99mmol) was added in four lots to above mixture and stirred at room temperature for 24 hours. After completion of the reaction, pour the reaction mass into water (250ml) while stirring. Filtered the product and dried to get the title compound (5.5 g). Example-13 Synthesis of 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)) To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of methanol slowly add sodium hydroxide (12 g, 0.3 mol), and cool the reaction mass to -15oC to -10oC. Slowly add cyanogen bromide (42 g, 0.4 mol) in methanol (60 ml) to the reaction mass over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (30 g, 80 % yield). Example-14: Synthesis of 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)) To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of methanol slowly add Potassium hydroxide (16.8 g, 0.3 mol), and cool the reaction mass to -15oC to -10oC. Slowly add cyanogen bromide (42 g, 0.4 mol) in methanol (60 ml) to the reaction mass over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (33 g, 88% yield). Example-15: Synthesis of 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)) To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of methanol slowly add Sodium carbonate (42.4 g, 0.4 mol), and cool the reaction mass to -15oC to -10oC. Slowly add cyanogen bromide (42 g, 0.4 mol) in methanol (60 ml) to the reaction mass over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (27 g, 72 % yield). Example-16: Synthesis of of 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)) : To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of methanol slowly add triethylamine (40.4 g, 0.4 mol), and cool the reaction mass to - 15oC to -10oC. Slowly add cyanogen bromide (42 g, 0.4 mol) in methanol (60 ml) to the reaction mass over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (25 g, 66.6 % yield). Example-17: Synthesis of of 2,4,4-trimethyl-7,2',4'-tricyanato flavan (Compound of Formula (Id)) : To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of DMF slowly add Sodium hydroxide (12 g, 0.4 mol), and cool the reaction mass to - 15oC to -10oC. Slowly add cyanogen bromide (42 g, 0.4 mol) in DMF (60 ml) to the reaction mass over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (31.5 g, 84% yield). Example-18: Synthesis of 2,4,4-trimethyl-7,2',4'-tricyanatoflavan (Compound of Formula (Id)) To the solution of 2,4,4-Trimethyl-7,2’,4’-trihydroxyflavan (30.0 g, 0.1mol), in 30 ml of methanol slowly add sodium hydroxide (12 g, 0.3 mol), Slowly add cyanogen bromide (42 g, 0.4 mol) in methanol (60 ml) to the reaction mass at the room temperature over a period of 60 minutes. Maintain the reaction mass at the same temperature for 4-5 hrs. After completion of the reaction (monitored by TLC), distill off methanol under vacuum and add 300 ml of water. Extract the product with MDC (3X100 ml) and wash the MDC layer with water (100 ml). Dry the MDC layer with sodium sulphate and distill-off solvent to get the title compound (28 g, 74.6% yield).