CYCLOADDITION REACTIONS OF TRANSITION-METAL 2-ALKYNYL COMPLEXES WITH A DISULFUR MONOXIDE SOURCE - TRANSITION-METAL-MEDIATED SYNTHESES OF 5-MEMBERED-RING THIOSULFINATE ESTERS

Reactions of cyclopentadienyl- and (pentamethylcyclopentadienyl)iron dicarbonyl 2-alkynyl complexes as well as cyclopentadienylmolybdenum tricarbonyl 2-alkynyl complexes with 4,5-diphenyl-3,6-dihydro-1,2-dithiin 1-oxide (37) have been shown to yield transition-metal-substituted five-membered-ring thiosulfinate esters in moderate to excellent yield. The transition metal can subsequently be cleaved from these cyclic metallothiosulfinate esters with ceric ammonium nitrate to yield carboethoxy-substituted five-membered-ring thiosulfinate esters. Reactions of chiral, racemic 2-alkynyl complexes with 37 also yield five-membered-ring thiosulfinate esters as the kinetic products of cyclization. The diastereoselectivity of these cycloadditions can be altered by the addition of MgBr2.