Lin L, Yamamoto K, Matsunaga S, * Kanai M. * The University of Tokyo and ERATO Japan
Science and Technology Agency, Tokyo, Japan
Rhodium-Catalyzed Cross-Aldol Reaction: In Situ Aldehyde-Enolate Formation from Allyloxyboranes
and Primary Allylic Alcohols.
Angew. Chem. Int. Ed. 2012;
51: 10275-10279
Key words
rhodium - aldol reaction - aldehydes - allylic alcohols - allyloxyboranes
Significance
Aldol reactions in which the aldol donor is derived from an aldehyde, are particularly
challenging. This report describes a strategy in which aldehyde enolates are generated
in situ by rhodium-catalyzed isomerization of triallylboroxanes. High syn-selectivity is obtained for a variety of aldehyde-donor and -acceptor partners.
Comment
Remarkably, the use of triallyloxyboranes is not required; simple primary and secondary
allylic alcohols also undergo the isomerization–cross-aldol sequence with similar
levels of reactivity and selectivity, presumably through a rhodium-enolate or -enol
mechanism.
