[2 + 3] Cycloadditions of Enantiomerically Pure Oxazoline N-Oxides: An Alternative to the Asymmetric Aldol Condensation
摘要:
A series of camphor-derived oxazoline N-oxides were obtained by condensation of the appropriate orthoesters with (+)-3-(hydroxyamino)borneol (8). These unstable dipoles were used without isolation in various [2 + 3] asymmetric cyclocondensations. The regio- and diastereoselectivities of these reactions were good to excellent. After functional group transformations, adducts were cleaved by a two--step sequence (i.e., oxidation followed by acidic hydrolysis) giving beta-hydroxy ketones and (+)-3-(hydroxyimino)borneol (19). Asymmetric synthesis of (+)-1,7-dioxaspiro[5.5]-undecan-4-ol, a pheromone of Dacus oleae, was achieved as an application of this new method.
[2 + 3] Cycloadditions of Enantiomerically Pure Oxazoline N-Oxides: An Alternative to the Asymmetric Aldol Condensation
摘要:
A series of camphor-derived oxazoline N-oxides were obtained by condensation of the appropriate orthoesters with (+)-3-(hydroxyamino)borneol (8). These unstable dipoles were used without isolation in various [2 + 3] asymmetric cyclocondensations. The regio- and diastereoselectivities of these reactions were good to excellent. After functional group transformations, adducts were cleaved by a two--step sequence (i.e., oxidation followed by acidic hydrolysis) giving beta-hydroxy ketones and (+)-3-(hydroxyimino)borneol (19). Asymmetric synthesis of (+)-1,7-dioxaspiro[5.5]-undecan-4-ol, a pheromone of Dacus oleae, was achieved as an application of this new method.
(+)-Norephedrine and (+)-camphor oxazolinesN-oxides 9a, 9b and 13a, 13b underwent regio- and stereoselective [2+3] cycloadditions on various electron poor dipolarophiles.
[2 + 3] Cycloadditions of Enantiomerically Pure Oxazoline N-Oxides: An Alternative to the Asymmetric Aldol Condensation
作者:Thierry Berranger、Yves Langlois
DOI:10.1021/jo00111a033
日期:1995.3
A series of camphor-derived oxazoline N-oxides were obtained by condensation of the appropriate orthoesters with (+)-3-(hydroxyamino)borneol (8). These unstable dipoles were used without isolation in various [2 + 3] asymmetric cyclocondensations. The regio- and diastereoselectivities of these reactions were good to excellent. After functional group transformations, adducts were cleaved by a two--step sequence (i.e., oxidation followed by acidic hydrolysis) giving beta-hydroxy ketones and (+)-3-(hydroxyimino)borneol (19). Asymmetric synthesis of (+)-1,7-dioxaspiro[5.5]-undecan-4-ol, a pheromone of Dacus oleae, was achieved as an application of this new method.
Stereoselective hetero-Claisen rearrangement of camphor derived oxazoline-N-oxides
作者:Peter I. Dalko、Yves Langlois
DOI:10.1016/s0040-4039(98)00062-8
日期:1998.4
Camphor derived oxazoline-hi-oxides in the presence of various acylating agents afforded alpha-acyloxyoxazolines resulting from a diastereoselective [3,3] rearrangement. The configuration of the newly formed asymmetric center was established by chemical correlation. The observed diastereoselectivity accounts a concerted rather than a stepwise process. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.