构象稳定的轴向手性硫乙内酰脲衍生物的羟醛反应,ACS Omega

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构象稳定的轴向手性硫乙内酰脲衍生物的羟醛反应
ACS Omega ( IF 3.7 ) Pub Date : 2021-10-15 , DOI: 10.1021/acsomega.1c03452
Sevgi Sarigul Ozbek ₁ , Melis Bacak Erdik ₂ , Ilknur Dogan ₂

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两种新型轴向手性邻已atroposelectively从反应制备三氟甲基苯基硫代海因衍生物ř和小号丙氨酸甲酯盐酸盐，与邻位的三乙基胺的存在三氟甲基苯基异硫氰酸酯。发现通过简单的重结晶纯化粗产物后，R氨基酸酯产生仅具有M轴手性的硫代乙内酰脲，而S仅返回P异构体。这一结果促使我们对M和P进行空间控制的羟醛反应乙内酰脲阻转异构体。结果发现，3-醛醇缩合反应过程中ö三氟甲基-5- methylthiohydantoins，所述Ó三氟甲基的基团的中号异构体有效地屏蔽了的Si中间的面并且以这种方式，使能仅选择性形成ř配置杂环 C5 处的羟醛产物。的P thiohydantoins，在另一方面，仅产生了小号C5配置羟醛产品为的结果重新面对屏蔽邻位中间烯醇化物的三氟甲基烷基。没有观察到苯甲醛分子的显着表面选择性（anti/syn只有 3/2) 在硫代乙内酰脲的三氟甲基苯基衍生物的醛醇缩合过程中。还使用先前合成的轴向手性硫代乙内酰脲与邻位-Cl、Br 和 I 苯基取代基进行羟醛反应，这些取代基主要具有P构象（P / M比 > 95%），并将立体化学结果与邻位-三氟甲基取代的。对于轴向手性邻卤苯基取代的乙内酰脲，观察到苯甲醛分子的 80-90% 面选择性。用轴向手性 3-邻-三氟甲基苯基-和 3-邻-iodophenyl-5-methyl thiohydantoins 能够立体选择性地在 thiohydantoin 环的 C5 处形成季铵化手性碳中心。

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Aldol Reactions of Conformationally Stable Axially Chiral Thiohydantoin Derivatives

Two novel axially chiral ortho-trifluoromethylphenyl thiohydantoin derivatives have been prepared atroposelectively from the reaction of R and S alanine methyl ester HCl salts with ortho-trifluoromethylphenyl isothiocyanate in the presence of triethyl amine. It was found that after purification of the crude product by simple recrystallization, the R amino acid esters yielded thiohydantoins having solely M axial chirality whereas the S ones returned the P isomers only. This result prompted us to perform sterically controlled aldol reactions on M and P thiohydantoin atropisomers. It was found that during the aldol reaction of 3-o-trifluoromethyl-5-methylthiohydantoins, the o-trifluoromethyl group of the M isomers efficiently shielded the Si face of the intermediate and in this way, enabled the selective formation of only the R configured aldol products at C5 of the heterocyclic ring. The P thiohydantoins, on the other hand, yielded only the S C5 configured aldol products as a result of the Re face shielding of the ortho-trifluoromethyl group of intermediate enolates. A noteworthy face selectivity of the benzaldehyde molecule was not observed (anti/syn only 3/2) during the aldolization of trifluoromethylphenyl derivatives of thiohydantoins. Aldol reactions were also done using the previously synthesized axially chiral thiohydantoins with ortho-Cl, Br, and I phenyl substituents which had predominantly P conformations (P/M ratios > 95%), and the stereochemical outcomes were compared with those of the ortho-trifluoromethyl substituted ones. 80–90% face selectivity of the benzaldehyde molecule was observed for the axially chiral o-halophenyl substituted thiohydantoins. The syntheses done with axially chiral 3-ortho-trifluoromethylphenyl- and 3-ortho-iodophenyl-5-methyl thiohydantoins enabled stereoselective formation of quaternized chiral carbon centers at C5 of the thiohydantoin ring.

更新日期：2021-10-26

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