Synthesis of new imidazole 3-Oxides; unexpected deoxygenation of some derivatives in the reaction with 2,2,4,4-Tetramethylcyclobutane-1,3-dithione

Abstract

Whereas the reaction of a series of 1,4,5-trisubstituted imidazole 3-oxides with 2,2,4,4-tetramethylcyclobutane-1,3-dithione gave the corresponding imidazole-2-thiones by a sulfur-transfer reaction via [2+3] cycloaddition, an unexpected deoxygenation occurred in the case of 4-acetyl- 1-(adamantan-1-yl)- 5-methylimidazole 3-oxide. It was shown that the presence of an electron- withdrawing substituent at C(4) and the bulky 1-adamantyl group at N(1) are necessary to enable this reaction course. A reaction mechanism via a zwitterion, followed by a 1,3-cyclization and elimination of an oxathiirane, is proposed