Carbenoid

In chemistry a carbenoid is a reactive intermediate that shares reaction characteristics with a carbene ["Organic Chemistry" john McMurry Brooks /Cole Publishing Company 1988 ISBN 0-534-07968-7] . 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 [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] .

:

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.

ee also

* The silicon pendant: Silylenoids

References