-Sigmatropic Rearrangement of an in Situ Prepared Ylide and a Thioether to Thio Ester Conversion as Key Steps in Short Syntheses of Sarkomycin and Its Phenylthio Ester

Article abstract of DOI:10.1021/jo00216a031

2-<(Phenylthio)methyl>cyclopent-2-en-1-one (2), which is readily available by the reaction of 2-cyclopentenone with thiophenol, formaldehyde, and triethylamine, is transformed, in high yield and moderate conversion by treatment with (trimethylsilyl)methyl triflate, cesium fluoride, and benzaldehyde, to 2-methylene-3-<(phenylthio)methyl>cyclopentanone (3), which, by the use of trichloroisocyanuric acid (Chloreal), can be quantitatively dichlorinated on the sulfur-bearing carbon atom to 3-<(phenylthio)dichloromethyl>-2-methylenecyclopentanone (4).This dichloro thioether could be hydrolyzed in good yield to a mixture of sarkomycin phenyl thio ester (5) and sarkomycin (6), containing mainly the former; an additional small amount of sarkomycin can be obtained by hydrolysis of the thio ester in the presence of silver trifluoroacetate and benzhydrol.This procedure represents one of the shortest extant syntheses of sarkomycin and a sarkomycin ester.Model studies of the dichlorination of n-octyl phenyl sulfide (8) to 1-(phenylthio)-1,1-dichlorooctane (9) and various transformations of the latter are also reported.