5-Isothiazolecarboxaldehyde → 4-(5-Isothiazolyl)-3-butenoic acid

Participants

Reaction Steps

Reaction of isothiazole-5-carboxaldehyde with lithium 3-(triphenylphosphoranylidene)propanoate under standard Wittig conditions provides 4-(5-isothiazolyl)-3-butenoic acid which is reduced and cyclized with aluminum chloride to provide 4-oxo-4,5,6,7-tetrahydrobenzisothiazole. The 4-oxo compound is reacted with methylenetriphenyl phosphorane under standard Wittig conditions and a methylene is inserted into the resulting 4-methylene compound via a Simmons Smith reaction to provide 6,7-dihydrospiro[benzisothiazol-4(5H),1'-cyclopropane] which is oxidized with hydrogen peroxide in acetic acid to give 6,7-dihydrospiro[3-oxo-benzisothiazol-4(5H),1'-cyclopropane 1,1-dioxide (4-spirocyclopropyl tetrahydrosaccharin). This is chloromethylated according to the procedure of Preparation 1A to give 2-chloromethyl-4-spirocyclopropyl-4,5,6,7-tetrahydrosaccharin.

Provenance & Evidence