Thiol Mediated Free Radical Cyclization of Alkenyl and Alkynyl Isocyanides
作者:Mario D. Bachi、Anna Balanov、Nira Bar-Ner
DOI:10.1021/jo00104a035
日期:1994.12
Thiol-mediated free radical cyclizations of but-3-enyl and but-3-ynyl isocyanides of types 6-8 give new access to 3,5-disubstituted 2-(alkyl- and 2-(arylthio)pyrrolines 11, 12, and 18. When 2-mercaptoethanol is used with the same isocyanides the reaction results in pyroglutamates 16, 17, or 19. These cyclizations involve the formation of a new carbon-carbon bond through intramolecular addition of a carbon-centered thioimidoyl radical to a carbon-carbon multiple bond. Although cyclic products are usually obtained in high yields, in a few cases a competing radical degradation process leading to isothiocyanates was observed. Isocyanide 8a carrying an allyl(phenyl) sulfide moiety isomerizes to 2-(phenylthio)pyrroline 24 in a series of sequential steps.
An alternative to the use of δ-lactam urethanes in the “ring switch” approach to higher homologues of AMPA-type glutamate antagonists
作者:Peter B. Hitchcock、Shazia Rahman (née Masood)、Douglas W. Young
DOI:10.1039/b304609p
日期:——
the preparation of homologues of AMPA-type glutamate antagonists, we have used 5-exomethylene derivatives of pyroglutamate esters. The homochiral pyrazole amino acid derivatives 18 and 19 have been prepared in this way. Although this synthesis yields products with a glycine residue separated from a heterocyclic ring by two carbon atoms, the substitution of the heterocyclic ring is different from that