An efficient synthesis of 2,3-dideoxy-α,β-unsaturated carbohydrate enals by mixed Lewis acid (HfCl4 and ZnI2) catalyzed hydration of glycals
摘要:
A new, efficient method has been developed for converting acyl-, arylalkyl- and alkyl-protected glycals into corresponding 2,3 -dideoxy-alpha, beta-unsaturated carbohydrate enals utilizing the in situ generated push-pull effect resulting from the synergistic combination of HfCl4 and ZnI2 in catalytic amounts. This new procedure eliminates the use of highly toxic Hg2+ ions and acidic conditions (0.01-0.02 N H2SO4), besides radically shortening the reaction time. (c) 2006 Elsevier Ltd. All rights reserved.
α,β-Unsaturated aldehydes bearing a δ-hydroxyl group undergo a tandem Michael and intramolecular Friedel–Crafts type cyclization with arylamines in the presence of 5 mol % of Bi(OTf)3 under mild conditions to afford a new class of chiral tetrahydroquinolines in good yields with high stereoselectivity. Structural assignments and the stereochemistry of the products was achieved using various 1D and 2D-NMR
Reinvestigation of the mercuration–demercuration reaction on alkylated glycals: an improved method for the preparation of 2,3-dideoxy-α,β-unsaturated carbohydrate enals
作者:Ram Sagar、Rashmi Pathak、Arun K Shaw
DOI:10.1016/j.carres.2004.05.027
日期:2004.8
Abstract Alkyl protected glycals can be easily converted into their corresponding α,β-unsaturated enals (Perlin aldehydes) in good to very good yields by reaction with HgSO 4 and aqueous 0.02 N H 2 SO 4 in THF or 1,4-dioxane. While the formation of Perlin aldehydes from benzyl-protected glucal and arabinal was accomplished by refluxing the reaction mixture in 1,4-dioxane, the benzyl-protected galactal
摘要与HgSO 4和0.02 NH 2 SO 4水溶液在THF或1,4-二恶烷中反应,可以很容易地将烷基保护的糖轻松地转化为相应的α,β-不饱和烯醛(Perlin醛)。通过将反应混合物在1,4-二恶烷中回流来完成由苄基保护的葡糖醛和阿拉伯糖生成Perlin醛的过程,而苄基保护的半乳糖和甲基保护的葡糖醛,半乳糖和阿拉伯糖在室温下从该反应中产生醛使用THF或1,4-二恶烷作为溶剂。