Direct Carbon−Carbon Bond Formation via Reductive Soft Enolization: A Kinetically Controlled syn-Aldol Addition of α-Halo Thioesters and Enolizable Aldehydes
摘要:
The direct addition of enolizable aldehydes and alpha-halo thioesters to produce beta-hydroxy thioesters enabled by reductive soft enolization is reported. The transformation is operationally simple and efficient and has the unusual feature of giving high syn-selectivity, which is the opposite of that produced for (thio)esters under conventional conditions. Moreover, excellent diastereoselectivity results when a chiral nonracemic alpha-hydroxy aldehyde derivative is used.
Direct Carbon−Carbon Bond Formation via Reductive Soft Enolization: A Kinetically Controlled syn-Aldol Addition of α-Halo Thioesters and Enolizable Aldehydes
摘要:
The direct addition of enolizable aldehydes and alpha-halo thioesters to produce beta-hydroxy thioesters enabled by reductive soft enolization is reported. The transformation is operationally simple and efficient and has the unusual feature of giving high syn-selectivity, which is the opposite of that produced for (thio)esters under conventional conditions. Moreover, excellent diastereoselectivity results when a chiral nonracemic alpha-hydroxy aldehyde derivative is used.
We found that the combination of Ph3P and TiCl4 was the excellent promoter for reductive Mannich-type reaction of S-2,4,6-triisopropylphenyl 2-bromopropanethioate with several imines and that the corresponding products were obtained in good yields with high anti-selectivity.
The Ph 3 P/TiCl 4 combination was found to be an effective promoter for the Claisen-type condensation of α-bromothioesters. Both in the case of self-condensation and crossed-type reactions, corresponding β-ketothioesters were obtained in good yields.
Phosphine/Lewis Acid Mediated Reformatsky-type Reaction of α-Bromoketone or -Thioester Derivatives
作者:Yukihiko Hashimoto、Satoshi Kikuchi
DOI:10.1246/cl.2002.126
日期:2002.2
The combination of (o-tolyl)3P/TiCl4 effectively promoted the Reformatsky-type reaction of α–bromoketone or -thioester derivatives with various aldehydes, and the corresponding β–hydroxy carbonyl compounds were obtained in good yield with high diastereoselectivity.
Direct Carbon−Carbon Bond Formation via Reductive Soft Enolization: A Kinetically Controlled <i>syn</i>-Aldol Addition of α-Halo Thioesters and Enolizable Aldehydes
作者:Scott J. Sauer、Michelle R. Garnsey、Don M. Coltart
DOI:10.1021/ja1057407
日期:2010.10.13
The direct addition of enolizable aldehydes and alpha-halo thioesters to produce beta-hydroxy thioesters enabled by reductive soft enolization is reported. The transformation is operationally simple and efficient and has the unusual feature of giving high syn-selectivity, which is the opposite of that produced for (thio)esters under conventional conditions. Moreover, excellent diastereoselectivity results when a chiral nonracemic alpha-hydroxy aldehyde derivative is used.