Highly Enantioselective Rhodium(I)-Catalyzed Activation of Enantiotopic Cyclobutanone C-C Bonds

Nicolai Cramer, Laetitia Marie Mélanie Souillart
Wiley-V C H Verlag Gmbh, 2014
Article

The selective functionalization of carbon-carbon sigma bonds is a synthetic strategy that offers uncommon retrosynthetic disconnections. Despite progress in CC activation and its great importance, the development of asymmetric reactions lags behind. Rhodium(I)-catalyzed selective oxidative additions into enantiotopic CC bonds in cyclobutanones are reported. Even operating at a reaction temperature of 130 degrees C, the process is characterized by outstanding enantioselectivity with the e.r. generally greater than 99.5:0.5. The intermediate rhodacycle is shown to react with a wide variety of tethered olefins to deliver complex bicyclic ketones in high yields.

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Nicolai Cramer, Laetitia Marie Mélanie Souillart
Wiley-V C H Verlag Gmbh, 2014
Article

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https://infoscience.epfl.ch/record/198336?ln=fr

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Enantioselective Rhodium-catalyzed C-C Bond Activation of Cyclobutanones

Nicolai Cramer, Laetitia Marie Mélanie Souillart

The activation of carbon-carbon bonds has attracted much attention in the past decade. Despite important progress, the development of asymmetric reactions lags behind. For the first time, asymmetric rhodium(I)-catalyzed direct oxidative additions into enantiotopic C-C bonds of cyclobutanones could be realized. Subsequent carboacylation of tethered olefins and carbonyl groups of the generated rhoda(III)cyclopentanone give an efficient access to complex polycyclic scaffolds in high yields. Despite operating at high reaction temperatures, the processes are characterized by outstanding enantioselectivities of generally greater than 99.5:0.5 er.

Swiss Chemical Soc2015

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Rhodium(I)-Catalyzed Enantioselective Activation of Cyclobutanols: Formation of Cyclohexane Derivatives with Quaternary Stereogenic Centers

Nicolai Cramer

The activation of carbon-carbon œÉ bonds is a complementary method to access uncommon and difficult-to-prep. organometallic species. Herein, we describe the activation of tert-cyclobutanols through an enantioselective insertion of a chiral rhodium(I) complex into the C-C œÉ bond of the cyclobutane, forming a quaternary stereogenic center and an alkyl-rhodium functionality that initiates ring-closure reactions. This technol. provides access to a variety of substituted cyclohexane derivs. with quaternary stereogenic centers. The formation of different product families can be controlled by the employed set of reaction conditions and additives. In general, high yields and excellent enantioselectivities of up to 99 % ee are obtained.

Wiley-VCH Verlag GmbH & Co. KGaA2010

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Catalytic Enantioselective Functionalizations of C-H Bonds by Chiral Iridium Complexes

Nicolai Cramer, Adrien Jules Louis Madron Du Vigné, Qui-Hien Nguyen, Jin Fay Tan, Lukasz Piotr Wozniak

The development of catalytic enantioselective transformations, enabling the construction of complex molecular scaffolds from simple precursors, has been a long-standing challenge in organic synthesis. Recent achievements in transition-metal catalyzed enantioselective functionalizations of carbon-hydrogen (C-H) bonds represent a promising pathway toward this goal. Over the last two decades, iridium catalysis has evolved as a valuable tool enabling the stereocontrolled synthesis of chiral molecules via C-H activation. The development of iridium-based systems with various chiral ligand classes, as well as studies of their reaction mechanisms, has resulted in dynamic progress in this area. This review aims to present a comprehensive picture of the enantioselective functionalizations of C-H bonds by chiral iridium complexes with emphasis on the mechanisms of the C-H activation step.

2020

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