Carbenoid

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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 by an insertion reaction into the C-B bond of a pinacol boronic ester [2].


Insertion of carbenoid into C-B bond

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