SU761462A1 - Method of preparing trans-cyclopentano-2,3-pyrrolidine - Google Patents

Description

The invention relates to an improved method for producing trans-cyclo-, pentano-2,3-pyrrolidine, which is an important starting compound 5 for the synthesis of alkaloids of nightshade species.

A method is known in the literature for the preparation of trans-cyclopentano-2,3-pyrrolidine by reductive amination of 2- (β-bromoethyl) -cyclopentanone with form- | 0 mid with the yield of the target product up to 20% [1).

However, if we take into account that the starting 2- (β-bromoethyl) -cyclopentanone, in turn, is obtained from cyclopentanone through three stages with a yield of 28%, then the total yield of trans-cyclopentano-2,3-pyrrolidine is only 5.6%.

The disadvantage of this method is the multi-stage process, 20 low yield of trans-cyclopentano-2,3-pyrrolidine and the inaccessibility of the starting products. ’

The purpose of the invention is to simplify the production process and increase the yield of 25 trans-cyclopentano-2,3-pyrrolidine.

The goal is achieved in that a mixture of cyclopentanone and _p-chloro ~ ethylamine in ether is treated with an alcohol solution of alkali at 30-35 C.

In this case, cyclopentano-Ζ, 3-Δ'-pyrroline is formed with a yield of 68%, which is then dissolved in methanol and reduced with metallic sodium ·.

‘The yield of the target product is 75.8%.

The total yield of Trans-cyclopentano-2,3-pyrrolidine by the proposed method from cyclopentanone is 51.5%.

The structure of the target product is confirmed by infrared spectroscopy and the preparation of crystalline derivatives.

Example. Trans-cyclopentano-2,3-pyrrolidine. Preparation of cyclopentano-2,2-th ^4- dyrroline. To a solution of 8.4 g (0.1 mol) of cyclopentanone in 100 ml of ether is added a solution of 7.6 g (0.1 mol) of β-chloroethylamine in 100 ml of ether (the extract after neutralization of ρ-chloroethylamine hydrochloride) and left overnight over caustic potassium. The next day, the solution is decanted and a solution of 6.7 g (0.12 mol) of potassium hydroxide and 20 ml of methanol is added with stirring. The reaction mixture is heated at 33-35 ° C for 4 hours. The precipitated salt (KC6) is filtered off. ,

..... 761462 the solvent (ether, methanol) is distilled off from the filtrate and distilled under vacuum. -;

7.2 g (68.0%) of cyclopentano-2, 341-43’C are obtained at 4 mmHg.

Δ-pyrroline with t ^ bale.

= 1.4946;

= 0.9451.

The IR spectrum has a clear absorption band in the region of 3 300 cm ' ¹ Ν-H bonds and there is no absorption band of C = I bonds.

According to published data, trans-cyclopentano-2 ^ 3-pyrrolidine has a bp of 60-61 C at 10 mm Hg;

cnaid. Found,%:

33.20; ^{ι Γ} 'τι comput.

= 32.80.

P ™ = 1.4868;

84 = 0.9473.

C ₇

12.77

Picrat, mp

-33.65; _isd 33.73.

90-91'C.

Calculated,%: N 12.74

In the IR spectrum there is a blanking band, which is characteristic for communication 1620-1630 ΟΝ of the connection.

Picrat, mp

78-80 ° C (from alcohol)

Recovery of cyclopentano-2,3-δ-pyrroline.

To a solution of g (0.065 mol) of cyclo'pentano-2,3-B-pyrroline in 50 ml of methyl alcohol, 20 g of 2.3 g (0.1 mol) of sodium metal are added in portions while stirring in small pieces. To complete the recovery at the end of the reaction, the mixture is heated in a water bath until sodium is completely dissolved.

After cooling (up to 20-25 ° C), 50 ml of dry ether are added to the 25th reaction mixture.

The precipitated sodium methylate is filtered off, the solvent (ether, methanol) is distilled off from the filtrate and the product is distilled off under vacuum.

Obtain 5.4 g (75.8%) of trans-cyclopentano-2,3-pyrrolidine with so Kip.

'51-53 “C at 7 mm Hg PD = 1.4865;

<33 ° = 0.9485. . 35

T.kip. 167-168 C at 764 mmHg Po = 1.4845; 84 = 0.930.

⁼ 34.1; _{b1 (h} - 3, 3.7; picrate, mp 87-90 ° C (from water). Using the proposed method makes it possible to obtain transcyclopentano-2, 3-pyrrolidine from the available starting products cyclopentanone and β-chloroethylamine with high yield (75.8% instead of 20%).

Claims (1)

Claim A method for producing trans-cyclopentano-2, 3-pyrrolidine based on cyclopentanone, characterized in that, in order to simplify the process and increase yield, the mixture of cyclopentanone and β-chloroethylamine in ether is treated with an alcohol solution of alkali at 30-35 * C, followed by restoration of the resulting while cyclopentane-2,3- {Y-pyrroline in methanol with sodium metal. = 33.91; MK; NU ^ MS * · = 33.73. ME LF "A. Found,%: N 12.42. C ₇ H <2 N. Calculated,%: N 12.60. ’............... Picrat. so pl. 90-91 ° C (from water).