The highly syn-selective Michael reaction of enamines with 2-(1-alkenyl)-1,3-dioxolan-2-ylium cations generated from 2,2-dimethoxyethyl 2-alkenoates in situ
2-Dimethoxyethyl 2-alkenoates are easily transformed into 2-(1-alkenyl)-1,3-dioxolan-2-ylium cations in situ on the action of titanium tetrachloride, which react with enamines to predominantly give syn Michael adducts in good yields. This is the first example of such a high syn-selectivity for the Michael reaction of α,β-unsaturated ester derivatives with ketone enolate equivalents.
Michael Addition of Ketone Enolates to α,β-Unsaturated Esters or Amides in a One-Pot Procedure: Highly Efficient Effect of Lithium Salt Generated in situ on Organotin Enolate
Michaeladdition of a metal ketone enolate to an a,p-unsaturated ester is thermodynamically disfavored, and thus, isolated metal enolates with an equimolar amount of Lewis acids or additives are usually required. This work describes the methodology of one-pot Michaeladdition from the parent ketones and unsaturated esters to the products directly. The treatment of a parent ketone with sec-butyllithium
金属酮烯醇化物与 a,p-不饱和酯的迈克尔加成在热力学上是不利的,因此,通常需要分离的金属烯醇化物与等摩尔量的路易斯酸或添加剂。这项工作描述了将母体酮和不饱和酯直接添加到产品中的一锅迈克尔加成方法。用仲丁基锂和 Bu 3 SnBr 处理母体酮得到高度配位的锡烯醇化物,它与原位生成的 LiBr 络合。该物质具有反应性,并在分别与 α,β-不饱和酯和酰胺的反应中提供迈克尔加合物、δ-酮酯和酰胺。