2-Methoxy-2H-chromenes from 2-Bromophenols and 3-Trimethylsilyloxyacroleins The preparation of 2-methoxy-2H-chromenes 6 from 2-bromophenols 1 and 3-trimethylsilyloxyacroleins 4 as C3 anellation reagents is described. Heterocyclization involves C-C linkage of ortho-lithiated 2-phenoxytetrahydropyrans 3 with 3-trimethylsilyloxyacroleins 4, followed by cyclization of the intermediate γ-hydroxysilylenolethers as lithium alkoxides 5, induced by hydrogen chloride in methanol. o-Hydroxycinnamic aldehydes 7 are isolated upon workup with trifluoroacetic acid instead of hydrogen chloride.
由
2-溴苯酚和 3-三甲基
硅氧基
丙烯醛制备 2-甲氧基-2H-苯 描述了由
2-溴苯酚 1 和 3-三甲基
硅氧基
丙烯醛 4 作为 C3 嵌段试剂制备 2-甲氧基-2H-苯 6 的过程。异环化过程包括正交
硫化
2-苯氧基四氢吡喃 3 与 3-三甲基
硅氧基
丙烯醛 4 的 C-C 连接,然后在
甲醇中用
氯化氢诱导中间体δ-羟基
硅基烯醚环化为
锂烷氧基化合物 5。