Dual Catalysis in Enantioselective Oxidopyrylium-Based [5 + 2] Cycloadditions
摘要:
A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and a second achiral thiourea. Experimental evidence points to a new type of cooperative catalysis with each species being necessary to generate a reactive pyrylium ion pair that undergoes subsequent cycloaddition with high enantioselectivity.
聚乳酸(PLA)是一种完全可生物降解和可回收的塑料,由生物衍生的单体制成:它是一种循环经济型塑料。它的性质取决于其立体化学,等规聚乳酸显示出优异的热机械性能。在这里,描述了一种通过利用轮烷构象动力学来控制战术性的新手段。动态的非手性[2]轮烷可以显示出较高的等选择性(P i = 0.8,298 K),而无需任何手性添加剂,并且可以通过链端控制机制进行链合。有机催化的动态立体选择性可能适用于其他小分子和聚合催化剂。