Chloromethyllithium carbenoid has been chemoselectively added to cyclic enones (5-, 6- and 7-membered systems, including two natural products) to provide chloromethyl allylic alcohols. Under the optimized reaction conditions neither concomitant (n+1) homologation nor conjugate addition or Simmons-Smith-like cyclopropanation takes place. The presence of LiBr is estimated to play a dual role, namely as a carbenoid stabilizer and mild Lewis acid activator of the C=O group. Notably, the mesomeric effect caused by β-heteroatom-containing substituents promotes the attack of the reagent at the most activated position.

Chemoselective additions of chloromethyllithium carbenoid to cyclic enones: A direct access to chloromethyl allylic alcohols / V. Pace, L. Castoldi, W. Holzer. - In: ADVANCED SYNTHESIS & CATALYSIS. - ISSN 1615-4150. - 356:8(2014 May 26), pp. 1761-1766. [10.1002/adsc.201301042]

Chemoselective additions of chloromethyllithium carbenoid to cyclic enones: A direct access to chloromethyl allylic alcohols

L. Castoldi
Secondo
;
2014

Abstract

Chloromethyllithium carbenoid has been chemoselectively added to cyclic enones (5-, 6- and 7-membered systems, including two natural products) to provide chloromethyl allylic alcohols. Under the optimized reaction conditions neither concomitant (n+1) homologation nor conjugate addition or Simmons-Smith-like cyclopropanation takes place. The presence of LiBr is estimated to play a dual role, namely as a carbenoid stabilizer and mild Lewis acid activator of the C=O group. Notably, the mesomeric effect caused by β-heteroatom-containing substituents promotes the attack of the reagent at the most activated position.
allylic alcohols; chemoselectivity; chloro compounds; enones; lithium carbenoids;
Settore CHIM/06 - Chimica Organica
15-apr-2014
Article (author)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/890696
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