Cycloaddition Reactions of Thioxoacetate Esters With Unsymmetrical Dienes

[摘要] The Diels-Alder reaction of transient thioxoacetate esters, RO2C. CHS, generated under mild, basic conditions from the Bunte salts, RO2C.CH2SSO3Na, has been studied with a variety of unsymmetrical, conjugated dienes. Specifically, ethyl thioxoacetate was generated from the Bunte salt, EtO2C.CH2SSO3Na, and trapped with 1-methoxy-1,3-cyclohexadiene, ethyl 3,5-hexadienoate, and the dienamine derived from Pummerer's ketone. Methyl 2,4-hexadienoate did not act as an effective trapping agent under these conditions. The regiochemistry, stereochemistry, and relative yields of the cycloadducts from each unsymmetrical diene are discussed. The retro-Diels-Alder reaction has also provided a good method for the generation of thioxoacetate esters. Ethyl thioxoacetate was generated by thermal cleavage of the corresponding anthracene cycloadduct, and was trapped in situ with 1-methoxy-1,3-cyclohexadiene. Similarly, the cycloadduct of methyl 2,4-hexadienoate and methyl thioxoacetate was obtained in good yield using the corresponding anthracene adduct as a source of the thioaldehyde. An intramolecular Diels-Alder reaction has been carried out successfully. The anthracene adduct of 3,5-hexadien-1-yl thioxoacetate was prepared by esterification of the corresponding acid. This cycloadduct dissociated in toluene at 111

[发布机构] University:University of Glasgow

[关键词] Organic chemistry