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

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 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]

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

References
  1. Organic Chemistry john McMurry Brooks /Cole Publishing Company 1988 ISBN 0-534-07968-7
  2. Iterative Stereospecific Reagent-Controlled Homologation of Pinacol Boronates by Enantioenriched -Chloroalkyllithium Reagents Paul R. Blakemore and Matthew S. Burge J. Am. Chem. Soc.; 2007; 129(11) pp 3068 - 3069; (Communication) doi:10.1021/ja068808s
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