Aldehyde-Promoted Addition of 2-(Trimethylsilyl)thiazole to ?,??-Dialkoxy Ketones: A new way to branched-chain monosaccharides
作者:Michela Carcano、Andrea Vasella
DOI:10.1002/hlca.19980810510
日期:——
The reaction of 2-(trimethylsilyl)thiazole (2-TST) with several ketones was tested in the presence or absence of aldehydes. The keto aldehyde 5 (Scheme 2) was prepared from 1via the hydroxy aldehyde 4 in 3 steps. It reacted with 2-TST to give, after desilylation and acetylation, the bis-thiazole 6. The ketone 11, obtained from 4 in 3 steps, reacted with 2-TST to give, after desilylation, 12. The ketofuranose
在存在或不存在醛的情况下测试了2-(三甲基甲硅烷基)噻唑(2-TST)与几种酮的反应。酮醛5(方案2)是从1经由羟基醛4分3步制备的。在去甲硅烷基化和乙酰化后,它与2-TST反应生成双噻唑6。从3个步骤中的4个中获得的酮11与2-TST反应,进行甲硅烷基化后,得到12。酮呋喃糖17(方案3)与2-TST反应,仅生成更稳定的D-葡萄糖差向异构体18。在1当量的存在下,酮11(方案2)与2-TST的反应更快。酮醛5的结构分析表明,醛促进了2-TST向酮的间接和分子间加成。我们已经研究了几种醛对酮11和17与2-TST在不同温度和不同浓度的酮和醛下的反应速率的影响。亲电子醛,特别是2-氟苯甲醛(0.1当量),可以促进2-TST加到亲电子酮中。