S. Yamada et al., Asymmetric spirocyclization: A new type of acid-catalyzed intramolecular 1,4-addition to form carba-spirocyclic compounds, TETRAHEDRON, 54(51), 1998, pp. 15555-15566
Novel spirocyclization based on intramolecular 1,4-addition and its asymmet
ric version have been developed using a combination of Lewis acid and 1,2-d
iol. Treatment of five- and six-membered alpha,beta-unsaturated cyclic keto
nes having a 4-oxopentyl group at the beta-position with Lewis acid and eth
ylene glycol gave spiro[4.5]decane-2,7-dione and spiro[5.5]undecane-2,8-dio
ne, respectively. The asymmetric version of this reaction has been develope
d by using optically active 1,2-diol such as cyclohexane-1,2-diol to afford
the spirocyclic products of up to 85% e.e. (C) 1998 Elsevier Science Ltd.
All rights reserved.