(1<i>R</i>)-(+)-Camphor and Acetone Derived α′-Hydroxy Enones in Asymmetric Diels−Alder Reaction: Catalytic Activation by Lewis and Brønsted Acids, Substrate Scope, Applications in Syntheses, and Mechanistic Studies
作者:Patricia Bañuelos、Jesús M. García、Enrique Gómez-Bengoa、Ada Herrero、José M. Odriozola、Mikel Oiarbide、Claudio Palomo、Jesús Razkin
DOI:10.1021/jo9023039
日期:2010.3.5
enones as reaction partners of the Diels−Alder reaction are shown, with especial focus on their potentials and limitations in solving the above difficult cases. α′-Hydroxy enones are able to bind reversibly to both Lewis acids and Brønsted acids, forming 1,4-coordinated species that are shown to efficiently engage in these inherently difficult Diels−Alder reactions. On these bases, a convenient control
Diels-Alder反应构成了最强大,最趋同的C-C键形成转化之一,并且仍然是获得环己烯亚结构的特权途径,该环己烯亚结构广泛存在于天然产物和生物活性成分中。近年来,不对称的Diels-Alder催化方法取得了巨大进展,但仍然普遍存在固有的困难二烯-二烯亲和性组合,例如那些与环戊二烯相比反应活性较低的二烯或类似β-取代的丙烯酸酯和类似物的二烯亲和性。此处显示了作为Diels-Alder反应的反应伙伴的α'-羟基烯酮的主要特征,特别关注了它们在解决上述困难情况中的潜力和局限性。α'-羟基烯酮能够与路易斯酸和布朗斯台德酸可逆结合,形成了1,4-配位的物种,这些物种被证明可以有效地参与这些固有的困难的Diels-Alder反应。在这些基础上,可以使用樟脑衍生的手性α'-羟基烯酮模型(底物控制的不对称诱导)和路易斯酸或布朗斯台德酸催化,方便地控制反应的立体控制。作为这种方法的补充,还可以通过将简单