Asymmetric Synthesis of Bicyclic Ketones Having an Angular Substituent via Ti(II) Alkoxide-Mediated Tandem Cyclization of Trisubstituted Olefinic Substrates
作者:Hirokazu Urabe、Daigaku Hideura、Fumie Sato
DOI:10.1021/ol9904038
日期:2000.2.1
[reaction: see text] Angularly substituted, optically active bicyclic ketones of up to 94% ee were prepared by the Ti(II) alkoxide-mediated tandem cyclization of open-chain substrates, that is, 8-phenylmenthyl enynoates having a trisubstituted double bond.
6 with KH and 18-C-6 at room temperature gives the cyclopentenone 7 in good yields. Mechanistic analysis reveals that this is the first case of an anionic oxy retro-enereaction followed by a tandem intramolecular aldol condensation. Reaction: see text.