The α-alkylation of carbonyl sulfoxonium ylides: studies and applications in the synthesis of new sulfur heterocycles

The challenging direct alpha-alkylation of sulfoxonium ylides is demonstrated after a deep study with several electrophiles. Twenty-five alkylated ester sulfoxonium ylides could be prepared in 12-67% isolated yields, employing Michael acceptors as electrophiles. Interestingly, no product arising from the classical cyclopropanation reaction, commonly observed for the reaction between sulfur ylides and Michael acceptors, was observed. To demonstrate the applicability of these unprecedented and more decorated sulfoxonium ylides, new and medicinal-chemistry important sulfur heterocycles, such as 2-mercaptobenzothiazoles, 1,4-benzothiazin-3-ones, and coumarin derivatives, were prepared.