Enantioselective Rhodium-Catalyzed [2 + 2 + 2] Cycloadditions of Terminal Alkynes and Alkenyl Isocyanates: Mechanistic Insights Lead to a Unified Model that Rationalizes Product Selectivity
作者:Derek M. Dalton、Kevin M. Oberg、Robert T. Yu、Ernest E. Lee、Stéphane Perreault、Mark Emil Oinen、Melissa L. Pease、Guillaume Malik、Tomislav Rovis
DOI:10.1021/ja905065j
日期:2009.11.4
describes the development and scope of the asymmetric rhodium-catalyzed [2 + 2 + 2] cycloaddition of terminal alkynes and alkenyl isocyanates leading to the formation of indolizidine and quinolizidine scaffolds. The use of phosphoramidite ligands proved crucial for avoiding competitive terminal alkyne dimerization. Both aliphatic and aromatic terminal alkynes participate well, with product selectivity a function
Asymmetric Synthesis of Bicyclic Amidines via Rhodium-Catalyzed [2+2+2] Cycloaddition of Carbodiimides
作者:Robert T. Yu、Tomislav Rovis
DOI:10.1021/ja710065h
日期:2008.3.1
A highly enantioselective rhodium-catalyzed [2+2+2] cycloaddition of terminal alkynes and alkenyl carbodiimides has been developed. This reaction demonstrates the feasibility of olefin insertion into carbodiimide-derived metalacycles and provides a new class of chiral bicyclic amidines as the major products. An isonitrile migration process responsible for the formation of the minor cycloadduct can
Predictable and Regioselective Insertion of Internal Unsymmetrical Alkynes in Rhodium-Catalyzed Cycloadditions with Alkenyl Isocyanates
作者:Rebecca Keller Friedman、Tomislav Rovis
DOI:10.1021/ja903899c
日期:2009.8.5
A regioselective, rhodium-catalyzed cycloaddition between a variety of internal, unsymmetrical alkynes is described. We document the impact of both steric and electronic properties of the alkyne on reaction course, efficiency, and enantioselectivity. The substituent that better stabilizes a positive charge or the larger group, all else being equal, inserts distal to the carbonyl moiety in a predictable
Total Synthesis of Indolizidine Alkaloid (−)-209D: Overriding Substrate Bias in the Asymmetric Rhodium-Catalyzed [2+2+2] Cycloaddition
作者:Robert T. Yu、Ernest E. Lee、Guillaume Malik、Tomislav Rovis
DOI:10.1002/anie.200805455
日期:2009.3.16
an efficient [2+2+2] cycloaddition between terminal alkyl alkynes and alkenyl isocyanates (see scheme). The cycloaddition proceeds through a CO migration pathway, and facilitates a rapid four‐step asymmetric synthesis of indolizidine (−)‐209D.
对!你让我问好:在铑上使用手性联苯基亚磷酰胺配体提供了末端烷基炔烃和烯基异氰酸酯之间有效的 [2+2+2] 环加成(参见方案)。环加成通过 CO 迁移途径进行,并促进吲哚里西啶 (-)-209D 的快速四步不对称合成。
Enantioselective Synthesis of the Tricyclic Core of FR901483 Featuring a Rhodium-Catalyzed [2+2+2] Cycloaddition
作者:Tomislav Rovis、Stéphane Perreault
DOI:10.1055/s-0032-1316786
日期:——
Abstract An efficient approach to the tricyclic framework of FR901483 is described. The sequence features a [3,3]-sigmatropic rearrangement of a cyanate to an isocyanate, followed by its subsequent asymmetric rhodium-catalyzed [2+2+2] cycloaddition with a terminal alkyne for the synthesis of the indolizidine core. The aza-tricyclic core is completed using an intramolecular benzoin reaction to close