Inchemistry acarbenoid is areactive intermediate that shares reaction characteristics with acarbene.[1] In theSimmons–Smith reaction the carbenoid intermediate is azinc /iodinecomplex that takes the form of
This complex reacts with analkene to form acyclopropane just as a carbene would do.
Carbenoids appear as intermediates in many other reactions. In one system a carbenoid chloroalkyllithium reagent is prepared in situ from asulfoxide andt-BuLi which reacts the boronic ester to give an ate complex. The ate complex undergoes a 1,2-metallate rearrangement to give the homologated product, which is then further oxidised to a secondary alcohol.[2]
Theenantiopurity of the chiral sulfoxide is preserved in the ultimate product after oxidation of the boronic ester to thealcohol indicating that a true carbene was never involved in the sequence.