1.
J Org Chem
; 68(2): 641-3, 2003 Jan 24.
Artigo
em Inglês
| MEDLINE
| ID: mdl-12530902
RESUMO
Five ketones R1COCH2R2 (1a-e) were enolized in tetrahydrofuran solvent employing lithium arylamides with different electron-withdrawing and -donating substituents on the phenyl ring (4a-e). Enolate selectivity is unaffected by a moderate electron-releasing or -withdrawing group, but significantly enhanced by strong electron-withdrawing substituents to yield predominantly Z-enolate. Outstanding selectivity was achieved with lithium trichloroanilide (5) and lithium diphenylamide (6). The results are rationalized in terms of electronic effects on the tightness of the transition states.