G. G. Melikyan

Synthesis of 4,5-dihydrofuran derivatives by the reaction of acetoacetic ester with conjugated alkenynes

The regiochemistry of the reaction of acetoacetic ester with vinylacetylene, isopropenylacetylene, and vinylisopropenylacetylene in the presence of the manganese acetate/copper acetate oxidative system was studied. Derivatives of furan and 4,5-dihydrofuran were obtained as a result of oxidative cyclization of intermediate radicals that contain unsaturated groups in the α position. Data from the IR, UV, PMR, 13C NMR, and mass spectra of the synthesized compounds are presented.

Synthesis of (±)-cis-tetradec-5-en-4-olide — The racemate of the sex pheromone of the Japanese beetle

A three-stage method has been developed for the stereoselective synthesis of (±)-cis-tetradec-5-en-4-olide — the racemate of the sex pheromone of the Japanese beetlePopillia japonica C. The key reactions used were the stereoselective cis reduction of a triple bond with the aid of heterogeneous hydrogenation catalysts (zinc-copper couple, nickel boride, Lindlar catalyst) and the radical lactonization of conjugated systems by the action of acetic acid in the presence of manganese acetate.

Synthesis of 4,5-dihydrofuran derivatives. Stereochemical study of the reactions of 1,3-alkadienes with ?-dicarbonyl compounds

Abstract4,5-Dihydrofuran derivatives were obtained by the reaction of cis- and trans-1,3-alkadienes with carbonyl compounds in the presence of the manganese (III) acetate/copper (II) acetate oxidizing system. It was observed that in the case of cis-1,3-alkadienes, in contrast to trans-1,3-alkadienes, inversion of the cis double bond, the degree of which depends on the structures of the unsaturated and carbonyl components of the reaction, occurs. It was shown that the reaction of cis-1,3-dodecadiene with diethyl malonate leads to the corresponding 1,4-addition product.

Use of two-dimensional spectroscopy for the determination of the stereochemical structure of 3-carbethoxy-2-methyl-7a-(4-carbethoxy-5-methyl-2-furyl)-3a,4,5,6,7,7a-hexahydrobenzofuran

Homo- and heteronuclear two-dimensional correlation spectra, as well as J-resolved spectra with selective excitation, were used to analyze in detail the stereochemical structure of 3-carbethoxy-2-methyl-7a-(4-carbethoxy-5-methyl-2-furyl)-3a,4,5,6,7,7a-hexahydrobenzofuran, obtained by the reaction of cyclohexenyl-acetylene with acetoacetic ester in the presence of a manganese(III) salt. It was shown that the use of the long-range 13C-1H coupling constants is a very effective method for the determination of the conformation of the molecule. The stereochemical aspects of the reaction of cyclohexenylacetylene with acetoacetic ester is discussed.

Synthesis of 4,5-dih ydrofuran derivatives by the reaction of acetylace tone with conjugated alkenes

The reaction of the acetylacetonyl radical (generated from acetylacetone by the action of manganese acetate) with vinylacetylene, 2-vinylfuran, and butadiene Was studied. The reaction proceeds nonregioselectively with vinylacetylene: 3-acetyl-2-methyl-5-ethynyl- and 3-acetyl-2-methyl-5-(4′-acetyl-5′-methyl-2′-furyl)-4,5-dihydrofurans in a ratio of 1∶2.2 were isolated. The principal products in the reaction with 2-vinylfuran and butadiene were 3-acetyl-2-methyl-5-(2′-furyl)- and 3-acetyl-2-methyl-5-vinyl-4,5-dihydrofurans.