Sulfur-based mixed ylides: unlocking new reactivity paradigms in modern organic synthesis

Sulfur ylides, first reported by Ingold and Jessop in 1930, have long occupied a central position in organic synthesis owing to their ambiphilic character and diverse reactivity. In recent years, ylide chemistry has progressed beyond classical systems toward the development of mixed ylides, in which two distinct heteroatoms are incorporated within a single ylide framework. Among these, sulfur based mixed ylides have emerged as powerful and versatile intermediates. Their unique electronic structure enables polarity inversion at the α-carbon, allowing this position to exhibit both nucleophilic and electrophilic behavior and thereby granting access to a broad range of reactive intermediates, including carbenes, radicals, carbocations, and carbynes. The discovery of the first sulfur based mixed ylide in 2018 marked a significant milestone, opening new avenues for reactivity and selectivity. This Review summarizes recent advances in sulfur based mixed ylide chemistry, with particular emphasis on their mechanistic features, and applications in diverse organic transformations.