Griffith AK, Vanos CM, Lambert TH * Columbia University, New York, USA
Organocatalytic Carbonyl-Olefin Metathesis.
J. Am. Chem. Soc. 2012;
134: 18581-18584
Key words
carbonyl-olefin metathesis - hydrazines - cycloaddition - cycloreversion
Significance
Lambert and co-workers have developed a carbonyl-olefin metathesis catalyzed by a
bicyclic hydrazine. The reaction is based on the idea to replace the typically used
[2+2]-cycloaddition–cycloreversion approach with a [3+2] analogue, which is thermochemically
allowed. The reaction was found to require a bicyclic hydrazine as the bishydrochloride
in order to proceed and is essentially restricted to aromatic aldehydes due to the
many degradation pathways for aliphatic aldehydes in the presence of the hydrazine
catalyst. The authors propose a catalytic cycle, in which the observed E-selectivity is explained.
Comment
Metathesis reactions involving carbonyls are much less developed than reactions of
olefins and alkynes with themselves. This work by Lambert and co-workers will hopefully
encourage further developments in this field. Future challenges are the use of unactivated
acyclic olefins, leading to a fragment coupling reaction, and the development of
a desymmetrization of meso-cyclopropenes using an enantiomerically pure hydrazine catalyst or by replacing
the chloride counteranion with one of the recently established chiral counteranions,
such as BINOL-derived phosphates.
