Opening of tartrate acetals using dialkylboron bromide: evidence for stereoselectivity downstream from ring fission.
J Am Chem Soc
; 125(2): 428-36, 2003 Jan 15.
Article
em En
| MEDLINE
| ID: mdl-12517155
ABSTRACT
Johnson-type acetals derived from dimethyl tartrate give, after opening with Me(2)BBr and cuprate displacement, secondary alcohols with high diastereoselectivity (>301). The mechanism proposed for the induction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of the Lewis acid as a source of nucleophile and the stereospecific transformation of the resulting bromo acetal through an invertive and temperature-dependent process. The acetals are prepared by reaction of the desired aldehyde with dimethyl tartrate. Removal of the auxiliary is accomplished through SmI(2) reduction or by an addition-elimination protocol using methoxide.
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01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
J Am Chem Soc
Ano de publicação:
2003
Tipo de documento:
Article