Four-membered silacycles are a class of important small cyclic compounds in organosilicon chemistry, which also have many applications to organic, organometallic and polymer chemistry. Silacyclobutanes with one silicon atom in the ring can be synthesized by the Grignard reaction of γ-halopropylsilanes, cycloaddition of Si＝C bond containing species with alkenes and ring expansion of silacyclopropanes. Silacyclobutenes with one silicon atom in the ring can be synthesized by Si—C bond forming ring-closure mediated by organolithium or Grignard reagents, conversion of silacyclobutanes, insertion of silylene into C—H bond, cycloaddition of Si＝C bond containing species with alkynes, and intramolecular cyclization of bis(alkynyl)silanes. Due to the ring strain and Lewis acid character, silacyclobutanes and silacyclobutenes can undergo ring expansion reactions to afford five- and six-membered silacycles, or ring opening to give organosilicon molecules and materials as well as fulfill organic transformations under very mild conditions.

Key words: silacyclobutane, silacyclobutene, cycloaddition, ring-expansion, bis(alkynyl)silane