Efficient and practical synthesis of optically active 5-t-butyldimethylsiloxy-2-cyclohexenone as a convenient chiral 2,5-cyclohexadienone synthon
作者:Shinichi Hikichi、Georges P-J. Hareau、Fumie Sato
DOI:10.1016/s0040-4039(97)10206-4
日期:1997.12
An efficient and practical method for the preparation of opticallyactive 5-t-butyldimethylsiloxy-2-cyclohexenone (3), a convenient chiral 2,5-cyclohexadienone synthon, from readily available ethyl 4-chloro-3-hydroxy-butyrate (7) has been developed where Ti(II)-mediated intramolecular nucleophilic acyl substitution and FeCl3-mediated ring expansion are the key reactions. The synthesis of racemic 6
A remarkable cis selectivity has been observed in the 1,4-addition of lower order primary and secondary alkylcyanocuprates to 5-silyloxy- and 5-benzyloxy-substituted cyclohexenones. This enables the preparation of both enantiomers of the corresponding 5-alkyl-substituted cyclohexenones (S)- and (R)-3 by the reaction of the readily available 5-(tert-butyldimethylsiloxy)-2-cyclohexenone (1) with either the lower or higher order cyanocuprate. DBU=1,8-diazabicyclo[5.4.0]undec-7-ene.