Enantioselective Synthesis of 3‐Substituted Cyclobutenes by Catalytic Conjugate Addition/Trapping Strategies
作者:Changxu Zhong、Yingchao Huang、Haocheng Zhang、Qiang Zhou、Yu Liu、Ping Lu
DOI:10.1002/anie.201913825
日期:2020.2.10
A copper-catalyzed tandem process to generate chiral cyclobutene derivatives has been developed. It is based on an enantioselective conjugate addition or reduction of a cyclobutenone and sequential trapping with a chlorophosphate in a one-pot process. These phosphates are stable under mildly acidic conditions and serve as good electrophiles in Negishi coupling reactions.
Cu<sup>I</sup>-Catalyzed Asymmetric [3 + 2] Cycloaddition of Azomethine Ylides with Cyclobutenones
作者:Javier Corpas、Alberto Ponce、Javier Adrio、Juan C. Carretero
DOI:10.1021/acs.orglett.8b00936
日期:2018.6.1
The catalytic asymmetric 1,3-dipolar cycloaddition of cyclobutenones with azomethineylides provides straightforward access to densely substituted 3-azabicyclo[3.2.0]heptanes. In the presence of CuI/(R)-Fesulphos as the catalytic system, high levels of diastereoselectivity and enantioselectivity were achieved (up to 98% enantiomeric excess (ee)).
环丁烯酮与偶氮甲亚胺的催化不对称1,3-偶极环加成反应可直接获得致密取代的3-氮杂双环[3.2.0]庚烷。在Cu I /(R)-Fesulphos作为催化体系的存在下,实现了高水平的非对映选择性和对映选择性(对映体过量(ee)高达98%)。
Asymmetric [4 + 2] Annulation of Cyclobutenones and Pyrazolone 4,5-Diones: Access to Novel δ-Lactone-Fused Spiropyrazolones
developed, the asymmetric construction of six-membered oxa-spiropyrazolones is still a challenging task in organic synthesis. Herein, we describe the [4 + 2] annulation of cyclobutanones and pyrazoline-4,5-diones for the efficient synthesis of δ-lactone-fused spiropyrazolone derivatives with generally high yields and good enantioselectivities under mild conditions. The successful scale-up synthesis and further
Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4 pi-ring opening of cyclobutene followed by an 8 pi-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C-C bond of cyclobutenone.