Center for Catalysis, Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.
J Am Chem Soc. 2012 Feb 8;134(5):2543-6. doi: 10.1021/ja211878x. Epub 2012 Jan 27.
A new concept in organocatalysis allowing for the construction of cyclobutanes with four contiguous stereocenters with complete diastereo- and enantiomeric control by a formal [2 + 2]-cycloaddition is presented. The concept is based on simultaneous dual activation of α,β-unsaturated aldehydes and nitroolefins by amino- and hydrogen-bonding catalysis, respectively. A new bifunctional squaramide-based aminocatalyst has been designed and synthesized in order to enable such an activation strategy. The potential and scope of the reaction are demonstrated, and computational studies which account for the stereochemical outcome are presented.
提出了一种新的有机催化概念，通过形式上的[2+2]环加成反应，能够在完全非对映和对映控制下构建具有四个连续立体中心的环丁烷。该概念基于分别通过氨基和氢键催化同时双重激活α,β-不饱和醛和硝基亚烯烃。为了实现这种激活策略，设计并合成了一种新型的双功能酰亚胺基酰胺基手性催化剂。展示了该反应的潜力和范围，并提出了可以解释立体化学结果的计算研究。
