Regiochemical Switching in Diels−Alder Cycloadditions by Change in Oxidation State of Removable Diene Sulfur Substituents. Synthesis of Carbazoles by Sequential Heteroannulation and Diels−Alder Cycloaddition
作者:Thomas G. Back、Aleksandra Pandyra、Jeremy E. Wulff
DOI:10.1021/jo0268714
日期:2003.4.1
which were oxidized with DDQ to produce vinylogous 2-(phenylthio)indoles 8. The latter compounds underwent highly regioselective Diels-Alder cycloadditions with methyl propiolate in the presence of MeAlCl(2) or AlCl(3), with simultaneous elimination of benzenethiol, to afford methyl N-(carbobenzyloxy)carbazole-3-carboxylates 9 and, in some cases, the N-deprotected derivatives 11. This is the opposite
N-羰基苄氧基-o-碘苯胺与1-苯基硫-1,3-丁二烯的钯催化杂环化反应生成二氢吲哚7,用DDQ氧化生成二乙烯基2-(苯硫基)吲哚8。后一种化合物具有高度区域选择性Diels -在MeAlCl(2)或AlCl(3)存在下与丙酸甲酯进行Al醛环加成反应,同时消除苯硫醇,制得N-(羧苄氧基)咔唑-3-羧酸甲酯9,在某些情况下提供N-脱保护的衍生物11.这是因此,环加成的区域化学可以有效的二烯硫取代基的氧化态的适当选择控制8.相应的砜类似物先前观察到的是,相对的区域化学。