SU430096A1 - - Google Patents

Description

(54) METHOD FOR OBTAINING TETRAY-SUBSTITUTED FURANS

The invention relates to a new method for the preparation of tetra-substituted chemicals of: furans of the formulas where RI is methyl, phenyl, a-thienyl, a-seleniumio;

K / O c, 1 B 5

: - vmv;

Ra is methyl, phenyl;

RS and Rg are carbomethoxygroup.

Tetrase-positioned furans can be used as source compounds in the synthesis of tri- and disubstituted furans, as well as various condensed heterocyclic systems.

A method for preparing tetra-substituted furano-like structures by the interaction of cy.1fonium x keto.ylides with diethyl acid acetylidericarboxylic acid is known. However, the initial ketaylides, used by a known method, are hard-to-stand (obtained from sulfoxides and p-d-arbonyl compounds only in a measured yield).

In order to increase the yield of target products and simplify the process technology, a method was proposed for obtaining tetrazameidene furans by the interaction of stable selenial ylides (obtained from available p-dicarbopyl compounds of organic selenides dichlorides, yield 60-100%) with dimethyl ether of acetylenedicarboic acid. The process is carried out at reflux in a polar organic solvent (chloroform, dichloroethane, tetrahydrofuran) and 60-100 ° C.

Tetrahydroselenofen (seleiol .n) is used as an organic selepid in this reaction, since the yield of ylides and furans in this case is higher than with other seleioids, except that seleiolane is more easily regenerated from the reaction mixture during the last stage of the synthesis of furans. .

The structure of the obtained furans was confirmed by IR, UV and PMR spectra.

The yield, constants and results of elemental analysis of the obtained compounds are given in the table.

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Example I. A mixture of 0.01 mol of seleponium ylide and 4.26 g (0.03 mol) of acetylenedicarboxylic acid dimethyl ester in 50 ml of chloroform is heated under reflux until all the ylide is reacted (chromatographic control in that aluminum oxide layer, eluant - chloroform), about 10 hours. Chloroform is distilled off, selepolium (fraction 135-145 ° C) is collected, then unreacted acetylenedicarboxylate is distilled off in vacuo. The residue in the case of Ri R2 (see Table 1, 1a and 16) is purified with BOGGI (1a) or crystallization (16). In the case of using ylides obtained from asymmetric p-diketones, the residue is chromatographed on an alumina column (cm, mm, eluent - benzene), the relative content of isomeric furans I and II is estimated using the PMR spectra: signal c, 6 (HMDS) t to the methyl group in the a-position of the wagon "s I, and the signal from, 4, to the acetyl group B in the position of furans II.

Example 2. 2-M.methyl-3- (selenoenyl-2) -4,5 dicarbmethoxyfuran 1d.

From 1.05 g (0.003 mol) of tetramethyleneenelenium-aceto- (selenoenyl-2) -methylide, 0.94 g (89%) of a mixture of isomeric furans (60% d, and 40% Pd) is obtained. The crystallization of this mixture from carbon tetrachloride gave 0.51 g (47%) of 1d.

Prev Invention

Claims (2)

1. The method of producing tetra-substituted furans of the formulas V0ir-r 5 .R / R; " Kg where RI is methyl, phenyl, a-thienyl, a-selelenoyl; Ra is methyl, phenyl; Ro and Re are a carbomethoxy group, characterized in that, in order to increase the yield of the target product and simplify the process technology, selenonium ylides of the formula AT  g / sone, 3., where RS and R4 are alkyl and Ri and Ra have the indicated meanings or Ri and R2 together form a tetramethylene group, are reacted with acetylenedicarboxylic acid dimethyl ester when heated. 2. A method according to claim 1, characterized in that the process is conducted in a polar organic solvent medium.