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首页> 外文期刊>Chemistry: A European journal >Solvent-dependent enantiodivergence in the chlorocyclization of unsaturated carbamates
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Solvent-dependent enantiodivergence in the chlorocyclization of unsaturated carbamates

机译：不饱和氨基甲酸酯氯环化中依赖溶剂的对映体

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摘要

A remarkable solvent-controlled enantiodivergence is seen in the hydroquinidine 1,4-phthalazinediyl diether ((DHQD)_2PHAL)-catalyzed chlorocyclization of unsaturated carbamates. Eyring plot analyses of this previously unreported reaction are used to probe and compare the R- and S-selective pathways. In the CHCl_3/hexanes solvent system, the pro-R process shows a surprising increase in selectivity with increasing temperature. These studies point to a strongly solvent-dependent entropy-enthalpy balance between the pro-R and pro-S pathways. Two solvents, two enantiomers: Enantiodivergent hydroquinidine 1,4-phthalazinediyl diether ((DHQD) _2PHAL)-catalyzed chlorocyclization of unsaturated carbamates, controlled solely by the choice of solvent, yields oxazolidinones in high enantioselectivity (see scheme; DCDMH=1,3-dichloro-5,5-dimethyl hydantoin). The origin of the observed enantiodivergence is traced back to a solvent-selected entropy-enthalpy balance between pro-R and pro-S pathways that dictates the course of the reaction.
机译：在对苯二酚1,4-酞嗪二基二醚（（DHQD）_2PHAL）催化的不饱和氨基甲酸酯的氯环化反应中，溶剂控制的对映异构度显着提高。该先前未报道的反应的Eyring图分析用于探测和比较R和S选择性途径。在CHCl_3 /己烷溶剂系统中，pro-R工艺显示出随温度升高而选择性出乎意料的增加。这些研究表明pro-R和pro-S途径之间强烈依赖溶剂的熵焓平衡。两种溶剂，两种对映异构体：仅通过选择溶剂控制的对映体对苯二酚1,4-酞嗪二基二醚（（DHQD）_2PHAL）催化的不饱和氨基甲酸酯的氯环化反应，会产生高对映选择性的恶唑烷酮（参见方案; DCDMH = 1,3- 5,5-二甲基乙内酰脲）。观察到的对映发散的根源可以追溯到决定反应进程的pro-R和pro-S途径之间溶剂选择的熵-焓平衡。

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