Carbenoid

In chemistry a carbenoid is a reactive intermediate that shares reaction characteristics with a carbene ^[1]. In the Simmons-Smith reaction the carbenoid intermediate is a zinc / iodine complex that takes the form of

I-CH₂-Zn-I

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This complex reacts with an alkene to form a cyclopropane 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 a sulfoxide and t-BuLi which reacts by an insertion reaction into the C-B bond of a pinacol boronic ester ^[2].

The enantiopurity of the chiral sulfoxide is preserved in the ultimate product after oxidation of the boronic ester to the alcohol indicating that a true carbene was never involved in the sequence.

See also

• The silicon pendant: Silylenoids

References