Technical field:

[0001] The present invention relates to one step process for synthesis of β,γ- unsaturated ketones from aldehydes and compounds containing allylic carbons. Particularly, the present invention provides Pd/N-Heterocyclic carbene catalyzed synthesis of /?,y-unsaturated ketones.

Background:

[0002 J ?,y-unsaturated carbonyl compounds are versatile starting materials for variety of synthetic reactions and there are only few methods available for their synthesis in the literature.

[0003] Acylation . of allylic esters is a potent method for synthetically useful β,γ- unsaturated ketones. However, due to the electrophilic nature of the carbonyl functionality, generation of nucleophilic acyl species become usually difficult. However, few examples of such allylic acylations have been reported in the literature.

[0004] For example, acylzirconocene chloride (Hanzawa, Y.; Tabuchi, N.; Taguchi, T. Tetrahedron Lett. 1998, 39, 6249) and chromium carbene complexes (Sakurai, H.; Tanabe, K.; Narasaka, K. Chem. Lett. 1999, 309) have been employed as acylation reagents in palladium-complex catalyzed acylation of allylic acetates or bromides. However, these reactions results in acylation products as a mixture of regioisomers, which are difficult to separate.

[0005] An article titled "Palladium-Complex Catalyzed Acylation of Allylic Esters with Acylsilanes" by Obora, Y. et al in J. Am.Chem. Soc. 2001, 123, 10489 discloses palladium complex catalyzed acylation of allylic trifluoroacetates (2) with acylsilanes (1). The reaction affords ^-unsaturated ketones (3) in good yields as shown below in scheme 1 : O

. 11

R ¹ CSiMe ₃ COCF3

1

Scheme 1

[0006] Another article titled "Palladium-catalyzed coupling reaction of acyl chromate complexes and allylic bromides by Hidehero et al in Chemistry letters 1999, page 309- 310, discloses cross coupling reactions between acyl chromate complexes and allylic bromides under CO atmosphere in the presence of Pd(PPh ₃ ) ₄ to afford corresponding allylic ketones as shown in scheme 2.

Scheme 2

[0007] The prior arts as discussed above utilize complicated/unstable starting materials, catalysts and reaction conditions. Also, the other disadvantage is that the resultant acylation products are mixture of regioisomers, which are difficult to separate.

Therefore, there remains a need in the art to explore "synergistic catalysis" that can provide a protocol for an efficient synthesis of ?,y-unsaturated ketones that ameliorates the drawbacks of the prior art processes. Objective of invention

[0008] The main objective of the present invention is to provide one step process for synthesis of /^-unsaturated ketones from aldehydes and compounds containing allylic carbons.

[0009] Another objective of the present invention is to provide Pd/N-Heterocyclic carbene catalyzed synthesis of /?,y-unsaturated ketones.

Summary of invention:

[00010] Accordingly, the present invention provides one step ^' process for preparation of /?,y-unsaturated carbonyl compounds/unsymmetrical ketones (IV) comprising adding solution of an aldehyde (II) to a solution of Pd-complex, jV-Heterocyclic carbenes (NHC) (III), a base and activated allylic carbon compound (I) in an organic solvent maintained at 0°C further raising the reaction mixture to room temperature ranging between 20-35 °C followed by stirring for a period ranging between 5-24 h to obtain /^-unsaturated carbonyl compounds/unsymmetrical ketones (IV);

wherein, R , R represent -H, aromatics, heteroaromatics, cyclic, heterocyclic, alkenes, alkyls, alkynes etc.

X represent halogens, -OH, -OTs, -OMs, carbonates, acetates etc.

L*- Ligands (selected from phsosphine, nitrogen, oxygen etc.)

NHC- N-Heterocyclic Carbenes (HI):

Y- S or N

Z- any counter anion

Saturated/Unsaturated

R ³ -R ⁶ - Alkyls, aromatics, heteroaromatics, cyclic, heterocyclic

Additionally R ⁴ and R ⁵ can be -H

[00011] In one embodiment of the present invention representative compounds of β,γ- unsaturated carbonyl compounds/unsymmetrical ketones of formula (IV) are:

(E)-4-(benzo[d] [ 1 ,3]dioxol-5-yl)- 1 -(4-chlorophenyl)but-3 -en- 1 -one (1);

(E)-l-(4-nitrophenyl)-4-phenylbut-3-en-l-one (2);

(E)-4-(benzo[d] [1 ,3]dioxol-5-yl)- 1 -(4-isopropylphenyl)but-3-en- 1 -one (3);

' (E)-4-(benzo [d] [ 1 ,3 ]dioxol-5-yl)- 1 -(3-(trifluoromethyl)phenyl)but-3-en- 1 -one (4);

(E) methyl 4-(4-phenylpent-3-enoyl)benzoate (5);

(E)-4-(benzo [d] [ 1 ,3]dioxol-5 -yl)- 1 -(3 ,5 -bis(trifluoromethyl)phenyl)but-3 -en- 1 - one (6);

(E)- (E)-3-(4-(naphthalen-l-yl)but-3-enoyl)benzaldehyde (7);

(E)-4-(furan-2-yl)- 1 -(4-(phenylsulfonyl)pheny l)but-3 -en- 1 -one (8) ;

(E)-4-(4-(4-fluorophenyl)pent-3-enoyl)benzonitrile (9);

E)-4-(4-chlorophenyl)- 1 -(4-nitrophenyl)but-3-en- 1 -one (10);

(E)-l-(benzo[d][l,3]dioxol-5-yl)-4-phenylbut-3-en-l-one (11);

[00012] In an embodiment of the present . invention the Pd complex is selected from Pd(PPh ₃ ) ₄ , Pd(OAc) ₂ , PdCl ₂ (PPh ₃ ) ₂ , Pd ₂ (dba) ₃ , PdCl ₂ (PPh ₃ ) ₂ ferro, PdCl ₂ .

[00013] In an embodiment of the present invention N-Heterocyclic carbenes are selected from,

1 ,3 -bis(2,6-diisopropylphenyl)- 1 H- imidazol-3-ium chloride

cyclohepta[d]thiazol-3-ium perchlorate 3-(2,6-diisopropylphenyl)-5,6,7,8- tetrahydro-4H-cyclohepta[d]thiazol-3- ium perchlorate

[00014] In another embodiment of the present invention the base is selected from organic or inorganic bases either alone or in combination thereof.

[00015] In another embodiment of the present invention the organic base is selected from DBU, DABCO, TMEDA, 1-Methylpiperazine, DMAP, DIPEA, Pyridine, NaOAc, Et ₃ N, ammonia and the inorganic base is selected from alkali and alkaline earth metal hydroxides, carbonates, bicarbonates either alone or in combination thereof.

[00016] In still another embodiment of the present invention inorganic base is selected from the group consisting of K ₂ C0 ₃ , Cs ₂ C0 ₃ Ag ₂ C0 ₃ , K ₃ P0 ₄ and MgS0 ₄ .

[00017] In still another embodiment of the present invention the solvents are selected from polar and non-polar solvents selected from alcohols, hydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers, nitriles either alone or in combination thereof.

[00018] In still another embodiment of the present invention - solvent used is acetonitrile. [00019] In still another embodiment of the present invention yield of ?,y-unsaturated carbonyl compounds/unsymmetrical ketones (IV) is in the range of 46-73%.

Description of drawings: Representative spectra of compound 1

[00020] Fig 1 a show 1H NMR of compound 1.

[00021] Fig lb show ¹³ C NMR of compound 1.

[00022] Fig lc show DEPT spectra of compound 1.

Detailed Description of the Invention:

[00023] The invention will now be described in detail in its preferred and optional embodiments, so that various aspects thereof will be more clearly understood and appreciated.

Abbreviations:

DBU- l ,8-Diazabicyclo[5.4.0]undec-7-ene

DABCO- l,4-diazabicyclo[2.2.2]octane

TMEDA- Tetramethylethylenediamine

DMAP- Dimethylaminopyridine,

DIPEA- N,N-Diisopropylethylamine

AcCN- Acetonitrile

[00024] In line with the above need, the present invention provides hitherto unexplored N-heterocyclic Carbene (NHC) mediated acylation of activated allylic carbons with aldehydes in presence of Palladium-complex to provide value added corresponding /?,y-unsaturated carbonyl compounds/unsymmetrical ketones. Such combination of Palladium and NHC for synergistic catalysis has never been used to effect such transformation in the prior art.

[00025] Accordingly, in a preferred embodiment, the invention disclose Pd/NHC- catalyzed one step process for preparation of ^^-unsaturated carbonyl compounds/unsymmetrical ketones comprising adding solution of an aldehyde (II) to a solution of Pd-complex, NHC (III), a base and activated allylic carbon compound (I) in an organic solvent maintained at 0°C; raising the reaction mixture to room temperature followed by stirring at room temperature to obtain desired compound (IV); as shown in scheme 3. + H. Ύ R N ,HC _ (H-»I,)

,R ²

^ X ^ Base, Pd (L ^* ) ^

Scheme 3

wherein, R ¹ , R ² = -H, aromatics, heteroaromatics, cyclic, heterocyclic , alkenes, alkyl; alkynes etc.

X = halogens, -OH, -OTs, -OMs, carbonates, acetates etc.

L*- Ligands (selected from phsosphine, nitrogen, oxygen etc.)

NHC- N-Heterocyclic Carbenes (III):

Y- S or N

Z- any counter anion

Saturated/Unsaturated

R ³ -R ⁶ - Alkyls, aromatics, heteroaromatics, cyclic, heterocyclic

Additionally R ⁴ and R ⁵ can be -H

[00026] The Pd catalyst is selected from but not limited to Pd(PPh ₃ ) ₄ , Pd(OAc);

PdCl ₂ (PPh ₃ ) ₂ , Pd ₂ (dba) ₃ , PdCl ₂ (PPh ₃ ) ₂ ferro and PdCl ₂ . .

-heterocyclic carbenes are selected from but not limited to;

[00028] The base is selected from organic bases such as DBU, DABCO, TMEDA, 1- Methylpiperazine, DMAP, DIPEA, Pyridine, NaOAc, Et ₃ N, ammonia and the like; the inorganic base may be selected from alkali and alkaline earth metal hydroxides, carbonates, bicarbonates such as K ₂ C0 ₃ , Cs ₂ C0 ₃ Ag ₂ C0 ₃ , K ₃ P0 ₄ and the like either alone or in combination thereof.

[00029] The solvent for purpose of the invention may be selected from polar and non- polar solvents such as alcohols, hydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers, nitriles and the like either alone or in combination thereof.

[00030] In another embodiment, the present invention provide corresponding β,γ- unsaturated ketones in good to moderate yields using various allylic carbon compounds and aldehydes as shown in Table 1.

Table 1:

" ^" OC0 ₂ B + "Y ₀ " ²

— ^NH. AcCN, MgS0 ₄

Scheme 4 (General representative Scheme)

[00031] In one preferred embodiment, compound 8 is prepared (Scheme 4) by treating allyl carbonate with a solution of Pd(PPh ₃ ) ₄ in an organic solvent with stirring at 0 °C followed by sequential addition of NHC's salt, 4-(phenylsulfonyl)benzaldehyde in presence of an organic base. After stirring for 12 h at room temperature the reaction mixture is concentrated; loaded on silica gel column and purified by using solvent gradient of Pet Ether: Ethyl Acetate (1 :9) to yield desired compound 8, (E)-4-(furan-3- yl)-l -(4-(phenylsulfonyl)phenyl)but-3-en-l-one as colorless oil.

[00032] The compound may optionally be purified from suitable crystallization solvent(s) if it is solid.

[00033] The compound thus obtained is further characterized by Ή-NMR, ¹³ C-NMR and DEPT.

[00034] In another embodiment, ^^-unsaturated are used for the synthesis of fine chemicals and other complex structures.

[00035] The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the inve

0°C-rt, 12 h

AcCN, MgS0

Scheme 5 Examples:

Example 1: Representative experimental procedure

(E)-4-(furan-3-yI)-l-(4-(phenylsulfonyl)phenyl)but-3-en-l -one (8):

[00036] In an oven dried round bottom flask a solution of Pd(PPh ₃ ) ₄ (5 mg, 0.004 mmol ), NHC (5 mg, 0.013 mmol), MgSO (100 mg) and allyl carbonate (32 mg, 0.163 mmol) in acetonitrile was stirred at 0 °C for 5 minutes. This was followed by sequential drop-wise addition of solution of 4-(phenylsulfonyl)benzaldehyde (20 mg, 0.081 mmol) and 1 -methylpiperazine (3 mg, 0.016 mmol). The reaction mixture was allowed to come to room temperature. After stirring for 12 h at room temperature the reaction mixture was filtered through a pad of celite, and the solvent was removed under reduced pressure. The crude reaction mixture was directly loaded on silica gel column and purified by using solvent gradient of Pet Ether: Ethyl Acetate (1 :9) to yield desired compound as colorless oil (21 mg, 73 %).

Example 2:

Characterization Data of all Compounds:

[00037] All reactions were performed on 20 mg scale of aldehyde.

(i) (E)-4-(benzo[d][l,3]dioxol-5-yl)-l-(4-chIorophenyl)but-3-en- l-one (1):

[00038] Reaction Time: 18 h; Rfi 0.4 (1 :19 EtOAc.Pet Ether); White Solid; mp 84°- 86°C; 28.2 mg, 66 %; 'HNMR (500 MHz, CDC1 ₃ , TMS) δ 8.01 (d, J= 8.5 Hz, 2H), 7.42 (d, J = 8.5 Hz, 2H), 6.96 (d, J = 1.8 Hz, 1H), 6.85 (dd, J = 7.9, 1.5 Hz, 1H), 6.76 (d, J = 7.9 Hz, 1H), 6.64 (d, J = 15.9 Hz, 1H), 6.22 (dt, J = 15.9, 6.4 Hz, 1H), 5.96(s, 2H), 4.94(dd, J = 6.4, 1.2 Hz, 2H); ^,3 C NMR (125 MHz, CDC1 ₃ , TMS) δ 165.6, 148.1 , 147.7, 139.5, 134.5, 131.1, 130.6, 128.7, 121.6, 121.1, 108.3, 105.9, 101.2, 65.9.

(ii) (E)-l-(4-nitrophenyl)-4-phenylbut-3-en-l-one (2):

[00039] Reaction Time: 5 h; Rf 0.5 (1:19 EtOAc:Pet Ether); White Solid; mp 64°- 66°C; 23.3 mg, 66 %; 'HNMR (400 MHz, CDC1 ₃ , TMS) δ 8.23 (d, J= 9.0 Hz, 2H), 8.18 (d, J= 9.0 Hz, 2H), 7.43-7.18 (m, 5H), 6.70 (d, J = 15.8 Hz, lH), 6.34 (dt, J = 15.8, 6.5 Hz, 1H), 4.96 (d, J= 6.5 Hz, 2H); ¹³ C NMR (100 MHz, CDC1 ₃ , TMS) δ 164.5, 150.5, 135.9, 135.6, 135.3, 130.8, 128.7, 128.4, 126.7, 123.6, 122.3, 66.5.

(iii)(E)-4-(benzo[d][l,3 l)but-3-en-l-one (3):

[00040] Reaction Time: 18 h; Rf.0.5 (1:19 EtOAc:Pet Ether); White Solid; mp 60°- 62°C; 21.7 mg, 57 %; 1HNMR (400 MHz, CDC1 ₃ , TMS) δ 7.92 (d, J = 8.3 Hz, 2H), 7.22 (d,J = 8.3 Hz, 2H), 6.88 (d,J= 1.3 Hz, 1H), 6.77 (dd,J= 8.0, 1.2 Hz, 1H), 6.69 (d,J = 8.0 Hz, 1H), 6.57 (d, J= 15.8 Hz, 1H), 6.16 (dt, J = 15.8, 6.5 Hz, lH), 5.88 (s, 2H), 4.86 (dd, J= 6.5, 1.0 Hz, 2H), 2.95- 2.83(m, 1H ), 1.19 (d, J= 6.8 Hz, 6H); ¹³ C NMR (100 MHz, CDC1 ₃ , TMS) δ 166.5, 154.4, 148.0, 147.6, 133.9, 130.7, 129.8, 127.8, 126.5, 121.6,121.5,108.3,105.8,101.1,65.4,34.2,23.7.

(iv)(E)-4-(benzo[d][l,3]diox l-5-yl)-l-(3-(trifluoromethyI)phenyl)but-3-en-l-one

[00041] Reaction Time: 12 h; Rf.0.5 (1:19 EtOAc:Pet Ether);. White Solid; 21.9 mg, 46 %; ^! HNMR (400 MHz, CDC1 ₃ , TMS) δ 8.26 (s, 1H), 8.19 (d, J= 7.8 Hz, 1H), 7.75 (d, J = 8.0 Hz, 1H), 7.52 (t, J = 7.8 Hz, 1H), 6.89 (d, J = 1.5 Hz, 1H), 6.79 (dd, J = 8.0, 1.5 Hz, 1H), 6.70 (d, J= 7.8 Hz, 1H), 6.60 (d, J= 15.8 Hz, 1H), 6.16 (dt, J= 15.8, 6.6 Hz, 1H), 5.89 (s, 2H), 4.91 (dd, J = 6.6, 1.0 Hz, 2H); C NMR ( 100 MHz, CDC1 _3, TN 165.1 , 148.1, 147.8, 134.9, 132.9, 131.4 (d, J= 33.13 Hz), 131.1, 130.4, 129.5 (d, J = Hz), 129.0, 126.6 (d, J = 3.8 Hz), 123.7 (d, J = 272.8 Hz), 121.7, 120.8, 108.3, 1' 101.2, 66.2.

(v) (E)-methyl 4-(4-phenylpent-3-enoyl)benzoate (5):

[00042] Reaction Time: 12 h; Rf. 0.4 (1 : 19 EtOAc:Pet Ether); White Solid; mp 6 62°C; 16.9 mg, 47 %; 1HNMR (400 MHz, CDC1 ₃ , TMS) δ 8.08-8.01 (m, 4H), 7.37 (c 7.3 Hz, 2H), 7.31 -7.20(m, 3H), 5.96 (t, J= 6.8 Hz, 1H), 4.99 (d, J= 7.0 Hz), 3.88 (s, 2.12 (s, 3H); ¹³ C NMR (100 MHz, CDC1 ₃ , TMS) δ 166.3, 165.8, 142.5, 140.8, 1; 133.9, 129.6, 129.5, 128.3, 127.6, 125.9, 121.0, 62.6, 52.4, 16.3.

(vi) (E)-4-(benzo[d][l,3]dioxol-5-yl)-l-(3,5-bis(trifluoromethyl) phenyl)but-3- 1-one (6):

[00043] Reaction Time 12 h; Rf 0.4 (1 : 19 EtOAc:Pet Ether); Thick yellow oil; mg, 70 %; 1HNMR (500 MHz, CDC1 ₃ , TMS) S 8.44 (s, 2H), 8.00 (s, 1H), 6.90 (s, 6.80 (d, J= 8.0 Hz, 1H), 6.71 (d, J = 8.0 Hz, 1H), 6.62 (d, J = 15.8 Hz, 1H), 6.17 (d1 15.8, 6.7 Hz, 1H), 5.90 (s, 2H), 4.95 (d, 6.7 Hz, 2H), ¹³ C NMR (100 MHz, CI TMS) δ 163.8, 148.1 , 147.9, 135.6, 132.2 (d, J = 101.73 Hz), 131.3 (d, J = 218.9 132.2 (d, J= 33.9 Hz), 129.82 (d, J = 3.1 Hz), 126.4 (m), 122.8 (d, J = 272.8 Hz), l: 120.16, 66.9. ·

(vii) (E)-3-(4-(naphthaIen-l-yI)but-3-enoyl)benzaldehyde (7):

[00044] Reaction Time: 24 h; Rf. 0.3 (1 : 19 EtQAc:Pet Ether); Thick yellow oil; 20.9 mg, 56 %; 1HNMR (400 MHz, CDCI3, TMS) δ 10.02 (s, 1H), 8.50 (s,lH), 8.27 (d, J = 7.9 Hz, 1H), 8.01 (d, J = 7.6 Hz, 1H), 7.57 (t, J - 7.6 Hz, 1H), 7.36 (d, J = 7.3 Hz, 2H), 7.27 (t, J = 7.3 Hz, 2H), 7.20 (d, J= 7.3 Hz, 1H), 6.69 (d, J= 15.9 Hz, 1H), 6.35 (dt, J = 15.9, 6.7 Hz, 1H), 4.95 (d, J = 6.7 Hz, 2H); ¹³ C NMR (125 MHz, CDC1 ₃ , TMS) δ 191.4, 165.3, 136.5, 136.0, 135.3, 135.0, 133.1 , 131.4, 131.3, 129.3, 128.6, 128.2, 126.7, 122.7, 66.1.

viii) (E)-4-(furan-2-yl)-l-(4-(phenyIsulfonyI)phenyl)but-3-en-l-on e (8):

[00045] Reaction Time: 12 h; Rf. 0.5 (1 :6 EtOAc:Pet Ether); Thick oil; 20.9 mg, 73 %; 1HNMR (400 MHz, CDC1 ₃ , TMS) δ 6.25 (d, J = 8.3 Hz, 2H), 8.14 (d, J = 8.5 Hz, 2H), 8.04 (d, J = 8.3 Hz, 2H), 7.75-7.62 (m, 3H), 7.53 (s, 1H), 6.69 (d, J= 15.8 Hz, 1H), 6.48- 6.41 (m, 2H), 6.32 (dt, J = 15.8, 6.5 Hz, 1H), 4.97 (dd, J = 6.5, 1.2 Hz, 2H); ¹³ C NMR (100 MHz, CDCI ₃ , TMS) δ 165.2, 152.7, 146.8, 143.7, 142.1, 135.3, 134.7, 131.3, 130.5, 126.7, 128.7, 123.2, 122.2, 1 12.3, 1 10.1, 66.2.

(ix) (E)-4-(4-(4-fluoroph e (9):

[00046] Reaction Time: 18 h; Rf. 0.3 (1 :19 EtOAc:Pet Ether); Thick oil; 19.6 mg, 46 %; 'HNMR (500 MHz, CDC1 ₃ , TMS) δ 8.09 (d, J= 8.2 Hz, 2H), 7.68 (d, J= 8.2 Hz, 2H), 7.32 (J = 8.5, 5.5 Hz, 2H), 6.96 (t, J = 8.5 Hz, 2H), 5.89 (t, J = 8.5 Hz, 1H), 4.98 (d, J = 7.0 Hz, 2H), 2.10 (s, 3H); ¹³ C NMR (125 MHz, CDC1 ₃ , TMS) δ 164.9, 162,4 (d, J = 247.0 Hz), 140.2, 138.3 (d, J = 2.89 Hz), 134.1, 132.2, 130.1, 127.5 (d, J

120.5, 1 17.2 (d, J= 196.5 Hz), 1 15.2, 115.1 , 62.8, 16.4.

(x) (E)-4-(4-chlorophe -l-(4-nitrophenyI)but-3-en-l-one (10):

[00047] Reaction Time: 10 h; Rf. 0.5 (l : 19EtOAc:Pet Ether); Yellow Solid; mp 127°- 129°C; 23.9 mg, 60 %; 1HNMR (400 MHz, CDC1 ₃ , TMS) 3 8.30 (d, J = 9.16 Hz, 2H), 8.24 (d, J= 9.16 Hz, 2H), 7.35 (d, J= 9.16 Hz, 2H ), 6.72 (d, J= 15.6 Hz, 1H), 6.38 (dt, J = 16.0, 6.4 Hz, 1H), 5.02 (dd, J= 6.4, 1.2 Hz, 2H) ¹³ C NMR (100 MHz, CDC1 ₃ , TMS) δ 164.5, 150.6, 135.4, 134.4, 134.0, 133.9, 130.8, 128.9, 127.9, 123.6, 123.0, 66.2.

(xi)(E)-l-(benzo[d][l,3]di -l-one (11):

[00048] Reaction Time: 12 h; Rf. 0.4 (1 : 13 EtOAc:Pet Ether); Yellow Solid; mp 43°- 45°C; 22.7 mg, 64 %; HNMR (400 MHz, CDC1 ₃ , TMS) δ 7.69 (dd, J= 8.2, 1.2 Hz, 1H), 7.50 (d, J = 1.8 Hz, 1H), 7.43-7.38 (m, 2H), 7.35-7.28 (m, 2H), 7.28-7.24 (m, lH), 6.84 (d, J = 8.2 Hz, 1H), 6.72 (d, J - 16.0 Hz, 1H), 6.38 (dt, J = 16.0, 6.4 Hz, 1H), 6.03 (s, 2H), 4.94 (dd, J = 6.4, 1.3 Hz, 2H); ¹³ CNMR ( 100 MHz, CDC13, TMS) δ 165.7, 151.6, 147.7, 136.2, 134.2, 128.6, 128.1, 126.6, 125.4, 124.2, 123.3, 109.6, 108.0, 101.8, 65.5. Advantages of invention:

1. Versatile starting materials without requiring preactivation.

2. Mild process conditions

3. Room temperature process.

4. High regioselectivity and high functional group tolerance.

5. Provides synergistic, catalytic Pd/NHC environment friendly process.