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07 Dec 17:03

Rh-Catalyzed Chemo- and Enantioselective Hydrogenation of Allylic Hydrazones

by Qiupeng Hu, Yanhua Hu, Yang Liu, Zhenfeng Zhang, Yangang Liu, Wanbin Zhang

Abstract

A highly efficient P-stereogenic diphosphine–rhodium complex was applied to the chemo- and enantioselective hydrogenation of allylic hydrazones for the synthesis of chiral allylic hydrazines in 89–96 % yields and with 82–99 % ee values. This methodology was successfully applied to the preparation of versatile chiral allylic amine derivatives.

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Diphosphine does the trick: Catalyzed by a P-stereogenic diphosphine–Rh complex, allylic hydrozones were chemo- and enantioselectively hydrogenated to afford chiral allylic hydrazines with high yields and excellent ee values.

21 Jul 15:11

Medium-Ring Nitrogen Heterocycles through Migratory Ring Expansion of Metalated Ureas

by Jessica E. Hall, Johnathan V. Matlock, John W. Ward, Katharine V. Gray, Jonathan Clayden

Abstract

Simple benzo-fused nitrogen heterocycles (indolines, tetrahydroquinolines, and their homologues) undergo migratory ring expansion through deprotonation of their benzylic urea derivatives with lithium diisopropylamide (LDA) in the presence of N,N′-dimethylpropylideneurea (DMPU). The products of the reactions are benzodiazepines, benzodiazocines, and their homologues, with ring sizes of 8–12. The reactions tolerate a range of substituent patterns and types, and may exhibit enantiospecificity or diastereoselectivity. Considerable complexity is rapidly generated in an efficient synthesis of these otherwise difficult-to-obtain medium-ring nitrogen heterocycles.

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Ringing in ureas: Simple benzo-fused nitrogen heterocycles (indolines, tetrahydroquinolines, and their homologues) undergo migratory ring expansion under basic conditions to generate a range of medium-ring nitrogen heterocycles with ring sizes of 8–12. Considerable complexity is rapidly generated in an efficient synthesis of these otherwise difficult-to-obtain rings.

16 Dec 18:55

Rh(I)-Catalyzed Transformation of Propargyl Vinyl Ethers into (E,Z)-Dienals: Stereoelectronic Role of trans Effect in a Metal-Mediated Pericyclic Process and a Shift from Homogeneous to Heterogeneous Catalysis During a One-Pot Reaction

by Dinesh V. Vidhani, Marie E. Krafft and Igor V. Alabugin

TOC Graphic

The Journal of Organic Chemistry
DOI: 10.1021/jo402505f