Microwave-accelerated Wittig olefination of β-chloroacroleins
作者:Rabin Bera、G. Dhananjaya、Shambu Nath Singh、Rajender Kumar、K. Mukkanti、Manojit Pal
DOI:10.1016/j.tet.2008.12.036
日期:2009.2
The first microwave assisted Wittig reactions of beta-chloroacroleins with a stabilized ylide are described here. A combination of sodium ethoxide and toluene was found to be optimum and using this reaction condition a number of alkenyl-substituted benzopyran/benzo[b]oxepine/2-chromenone derivatives were prepared within few minutes. The microwave mediated process was found to be comparable with the conventional Wittig reaction in terms of product yields. All the products isolated were found to have E-geometry around the C=C bond. (C) 2008 Elsevier Ltd. All rights reserved.
The vilsmeier reaction in the synthesis of 3-substituted [1]benzopyrano[4,3-<i>b</i>]pyridin-5-ones. An unusual pyridine ring closure
作者:D. Heber、I. C. Ivanov、S. K. Karagiosov
DOI:10.1002/jhet.5570320221
日期:1995.3
the reaction of 4-chloro-3-vinylcoumarins 3a-d with primary amines 4a-h. The coumarin derivatives 5 (except 5k) underwent an unusual pyridine ring closure under Vilsmeier conditions to form the benzopyrano[4,3-b]pyridines 6. When the aminoaldehydes 7 were treated with the Wittig reagent 2b the fused N-alkyl-2(1H)-pyridinones 8 have been obtained as expected.
从4-氯香豆素-3-甲醛(1)和维蒂希( Wittig )膦烷2a-d开始,已经通过四步顺序合成了标题化合物6a-c。通过4-氯-3-乙烯基香豆素3a-d与伯胺4a-h的反应制备了中间体4-烷基氨基-3-乙烯基香豆素5a-k。香豆素衍生物5(5k除外)在Vilsmeier条件下经历了异常的吡啶环闭合,以形成苯并吡喃并[4,3- b ]吡啶6。用维蒂希试剂2b处理氨基醛7时如所期望的,获得了稠合的N-烷基-2 (1 H) -吡啶酮8。