The present invention relates to specific a,b-unsaturated carboxylates and a method of making them.

The specific a, b-unsaturated carboxylates which are aimed to be produced are represented by the following formula (I)

wherein

Ri is a Ci - C -alkyl moiety, preferably -CH ₃ or -CH ₂ CH ₃ , and

R ₃ is one of the following groups

wherein

R ₄ is CH ₃ or phenyl

(the * is showing where the bond is localized). These specific a,b-unsaturated carboxylates are useful compounds. They can be used as such or they are useful intermediates to produce other compounds. For example compound (la)

is used as an intermediate in the production of Vitamin A acetate (via a reduction followed by an acetylation)

Therefore due to the importance of such important intermediates, there is always a need for improved methods of producing such compounds.

The compounds of formula (I) are not known from the prior art.

Therefore the present invention relates to compounds of formula (I)

wherein

Ri is a Ci - C4-alkyl moiety, preferably -CH3 or -CH ₂ CH3, and

(the * is showing where the bond is localized), and

R ₃ is one of the following groups

wherein

R is CH ₃ or phenyl

(the * is showing where the bond is localized).

Preferred are compounds of formula (I), wherein

Ri is-CHs or -CH ₂ CH ₃ .

Therefore the present invention relates to compounds of formula (la), which are compound of formula (I), wherein Ri is-CH ₃ or -Ch CH _!

Preferred are compounds of formula (I), wherein

Therefore the present invention relates to compounds of formula (lb), which are compounds of formula (I) or (la), wherein

Preferred are compounds of formula (I), wherein

R ₃ is one of the following groups Therefore the present invention relates to compounds of formula (lc), which are compounds of formula (I), (la) or (lb), wherein

R ₃ is one of the following groups

Most preferred are the following compound of formulae (G) to (I””)

The compounds according to the present invention are produced using commonly known processes.

A preferred process to produce these compounds is the following

A compound of formula (II) having a terminal C-C triple bond is reacted with a specific carboxylic acid. The substituents Ri , R ₂ and R ₃ have the same meanings (and the same preferred meanings) as defined above.

The reaction is carried in the presence of a specific catalyst (Cat) which has the following formula (IV)

wherein

R5, Re, R7, and Rs signify -CH3, -OCH3, -NO ₂ , halogen or -H, and

X and Y signify independently from each other an allylic moiety, and

q signifies an integer 1 , 2 or 3.

A very preferred catalyst is the one of formula (IVa)

The substrate (Compound of formula (II) to catalyst ratio (mol-based) is usually from 5000 : 1 to 10 : 1 , preferably from 1000 : 1 to 20 : 1. The process according to the present invention is carried out without any solvents or in at least one apolar aprotic organic solvent. All reactants are added together and mixed. The reaction mixture is heated to the temperature at which the transition metal-based catalytic rearrangement reaction occurs, to provide a resulting mixture.

As solvents there can be used in the scope of the present invention in general apolar aprotic organic solvents, especially aliphatic, cyclic and aromatic hydrocarbons, such as, for example, C ₇ -Cio-alkanes, C ₅ -C ₇ -cycloalkanes, benzene, toluene and naphthalene as well as mixtures of such solvents with one another, e.g. paraffin oil (a mixture of saturated aliphatic hydrocarbons). As well as carboxylate esters, such as ethyl acetate. The process according to the present invention is usually carried out under very mild reaction condition. The reaction temperature is usually between -5°C and 60°C. Preferably between 0° and 50°C.

The following Example illustrates the invention further without limiting it. All per-centages and parts, which are given, are related to the weight and the tempera-tures are given in °C, when not otherwise stated.

Examples

Example 1 : 3-Methyl-1-(2,6,6-trimethylcyclohex-1 -en-1 -yl)pent-1-en-4-yn-3-ol (2.33 g, 10 mmol) and 1- adamantanecarboxylic acid (2.73 g, 15 mmol, 1.5 eq.) were dissolved in anhydrous ethyl acetate (10 mL) under argon atmosphere. In a counter flow of argon, 61 mg (0.1 mmol, 1.0 mol%) of the ruthenium catalyst of formula (IVa) were added. After stirring for 3 h at 20°C , the light yellow-brown reaction mixture was concentrated under reduced pressure (rotavap, 20°C water-bath temperature). The crude product was dried for another 2 h at 20 mbar resulting in a light brown oil.

The product of formula (I””)

Example 2: 3-Methvl-5-(2, 6, 6-trimethylcyclohex- 1 -enyl) penta-2, 4-dienal

3-Methyl-1-(2,6,6-trimethylcyclohex-1 -en-1 -yl)pent-1-en-4-yn-3-ol (2.26 g, 10 mmol) and 2,2-dimethylpropanoic acid (1.53 g, 15 mmol, 1.5 eq.) were mixed under argon atmosphere. In a counter flow of argon, 122 mg (0.2 mmol, 2.0 mol%) of the ruthenium catalyst of formula (IVa) were added. After stirring for 18 h at 20 °C, 20 ml of ethyl acetate and 10 % sulfuric acid (150 mI_) were added drop wise. After one hour at 24 °C the reaction was complete and the reaction mixture was washed once with semi saturated sodium bicarbonate (80 mL) and once with water (40 mL). The aqueous layers were re-extracted twice with ethyl acetate (40 mL). The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure (rotavap, 30 °C water-bath temperature). The crude product compound of formula (I’”) was dried for another 2 h at 20 mbar resulting in a red-brown oil (2.76 g, 74 % purity, 94 % yield). In the following table more compounds of formula (I) have been produced by the same way as in Example 1 and 2. Other carboxylic acids have been used and/or the reaction time and/or the reaction temperature and/or the amount of ethyl acetate (solvent) have been varied. Table 1 :