CH645338A5 - ESTERS OF THE 2,2-DIMETHYL-3-ACETOXY-METHYL-CYCLOPROPANCARBOXYLIC ACID AND THEIR PREPARATION. - Google Patents

Description

The present invention relates to esters with lower alcohols of 2,2-dimethyl-3-acetoxymethyl-cyclopropancarboxylic acid and their preparation method.

20 The above compounds, having general formula

H3C

H C-C-O-CH - CH

a fl a

X

CH - COOR CD

30

(where R = lower alkyl)

they are useful intermediates for the synthesis of pyrethroid insecticides.

In fact, by simple hydrolysis the compounds of formula (I) are transformed into 2,2-dimethyl-3-hydroxymethyl-cyclo-35 propancarboxylic acid (II) and this by oxidation provides the caronaldehyde (2,2-dimethyl-3- acid formyl-cyclopropancarbos-silico) (III) from which it is possible to obtain chrysanemic acid (TV) by reaction with isopropyliden-triphenylphospho-rano [see for example Tetrahedron Letters 43, 3915 (1976)]

H3C

(I>

hydrolysis

- * HOCH - CH

ck

V

/ \

CH,

- CH - COOH

(II)

(II)

oxidation

H3C

/ \

C - CH - CH - COOH

II

(III)

HC CH.

3 \ / 3

, Tm isopropyliden-phosphorane H3C \, "

(III) 1 ^ C = CH-CH - CH-COOH (IV)

HC /

3

3

645338

The compounds of the general formula form the subject of the present invention:

H.C, CH,

or v

/ \

H C-C-O-CH - CH -

O fi C »

0

CH - COOR (I)

wherein R = lower alkyl.

The preparation of the compounds of formula (I), which constitutes a second object of the present invention, is carried out by reacting the prenyl acetate (3,3-di-15 methyl-allyl acetate) (V) with diazoacetate (VI) .

"3C

\

H3C

/

C = CH-CH -O-C-CH (V) + N CH-COOR (VI)

M || O (Z

->

(THE)

0

(wherein R = lower alkyl).

The above reaction is carried out in an inert solvent such as cyclohexane and in the presence of anhydrous copper sulphate and powdered metallic copper as catalysts.

The amount of anhydrous copper sulphate used is about a tenth of a mole per mole of prenyl acetate.

Metallic copper is used in approximately the same amount as copper sulphate.

In a practical embodiment, the reaction is carried out by slowly adding a slight excess of diazoacetate dissolved in cyclohexane to a suspension of copper and metallic copper sulphate in cyclohexane already containing the predetermined amount of prenyl acetate.

The whole is kept under a light stream of nitrogen and heated to a slight reflux (about 80 ° C).

Once the addition of the diazoacetate has been completed, the reaction mixture is left for a few minutes under reflux and is then processed according to normal laboratory techniques.

After elimination of the solvent, a crude is obtained which is subjected to distillation to collect the product.

With the aim of better illustrating the invention, the following examples are now provided.

35

Example 1

Preparation of the ethyl ester of 2,2-dimethyl-3 -acetoxymethyl-cyclopropanecarboxylic acid. 50

H3C

h3c

\ /

C = CH-CH -O-C-CH "+ N OH-COOC H 2 11 3 2 2 5

(1)

0

(2)

HC CH 3 \ / 3

•> H C-C-O-CH -CH

3 u 2

TO

- CH - COOC H 2 5

(3)

645338

4

In a flask equipped with a stirrer, drop, thermometer and drip funnel, 0.6 moles of prenyl acetate, 0.07 moles of anhydrous copper sulphate, 0.05 moles of copper powder and 340 cc of cyclohexane are placed. The suspension is heated to a slight reflux (about 80 ° C). 0.72 moles of ethyl diazoacetate mixed with 300 cc of cyclohexane are added under a light stream of nitrogen, by dripping in about 2 hours. During the dripping, the external heating is decreased in order to maintain the reaction at gentle reflux. Once the drip is finished, the mixture is kept for 10 minutes and then filtered, the salt is washed with 2 portions of 30 cc of cyclohexane, the organic phases are washed together with water (3 X 100 cc), anhydrified on sodium sulphate and the solvent is eliminated by evaporation at 15 mmHg and 40 ° C. The reaction raw product (weight 140-150 g) is distilled at 0.1 mmHg / 75 ° -80 ° C, obtaining compound 3 with yields between 55 and 60%.

The NMR (Nuclear Magnetic Resonance) analysis showed that the ratio between the eis and trans isomers is about 1: 1.

Infrared analysis highlights significant bands at 1720, 1380, 1240, 1175 and 1025 cm "1.

Example 2

The purpose of the present example is to show the preparation of lower alkyl esters of 2,2-dimethyl-3-hydroxymethyl-cyclopropanecarboxylic acid starting from the compounds prepared by means of the process object of the invention.

To a solution of 0.2 g of sodium (0.01 moles) in 100 ml 5 of absolute ethyl alcohol kept under stirring at room temperature, a solution of 10.7 g (0.05 moles) of 2 is slowly added, Ethyl 2-dimethyl-3-acetoxymethyl-cyclopropan carboxylate (prepared as described in Example 1) in 20 ml of ethyl alcohol.

The reaction mixture is then left under stirring overnight at room temperature then the solvent is removed by distillation under reduced pressure.

The residue is taken up in 200 ml of ethyl ether and 20 ml of water.

i5 The organic phase is separated, anhydrified with anhydrous Na2SO4 and the solvent is removed by distillation.

The residue is distilled under reduced pressure collecting the fraction boiling at 100-108 ° C at a pressure of 1.6 mmHg. Said fraction consists of the compound 2,2-dimethyl-20 -3-hydroxymethyl-cyclopropanecarboxylate of ethyl (Infrared analysis consistent with the assigned structure).

The oxidation of the above compound to caronaldehyde can be carried out according to known techniques [Journal of Organic Chemistry, pag. 885 (1976)].

v

Claims (9)

645338 2. A compound according to claim 1, wherein the compound of formula (I) is the ethyl ester of 2,2-dimethyl-3-acetoxymethyl-cyclo-propancarboxylic acid. 2 CLAIMS 1. Compounds of general formula: , CH H3C X H C-C-O-CH - CH - U fi W OR wherein R = lower alkyl. 3. Process for the preparation of the compounds of claim 1, characterized in that the 3,3-di-methyl-allyl acetate is reacted with a diazoacetate of formula: N2CH - COOR (VI) (where R = lower alkyl) in an inert solvent and in the presence of anhydrous copper sulphate and metallic copper powder. 4. Process according to claim 3, characterized in that cyclohexane is used as the solvent. 5 characterized in that the reaction between the 3,3-di-methyl-allyl acetate and the diazoacetate is carried out by adding a solution of the latter in cyclohexane to a suspension of copper sulphate, metallic copper and acetate of 3, 3-di-CH - COOR (I) methyl allyl in cyclohexane kept under stirring in a nitrogen atmosphere at 80 ° C. 5. Process according to claims 3 or 4, characterized in that the copper sulphate is used in a molar ratio of about 1 to 10 with respect to the 3,3-dimethyl-allyl acetate. Process according to one of claims 3, 4 or 5, characterized in that the metallic copper is used in a molar ratio of about 1 to 10 with respect to the 3,3-di-methyl-allyl acetate. Process according to one of claims 3 to 6, characterized in that the reaction between the 3,3-di-methyl-allyl acetate and the diazoacetate is carried out at about 80 ° C. 8. According to one of claims 3 to 7, Process according to one of claims 3 to 8, characterized in that the diazoacetate of formula (VI) is ethyl diazoacetate.