Rhodium-catalyzed ortho C–H bond activation of arylamines for the synthesis of quinoline carboxylates
作者:Sunita K. Gadakh、Soumen Dey、A. Sudalai
DOI:10.1039/c6ob00170j
日期:——
The rhodium catalyzed annulation of anilines with alkynic esters allowing for the high-yieldsynthesis of quinoline carboxylates with excellent regioselectivity is described. This unprecedented reaction employs either formic acid as the C1 source and reductant or copper(II) as the oxidant and is proposed to proceed via rhodacycle of in situ generated amide and enamine ester followed by ortho C–H activation
Multicomponent reactions (MCRs), followed by subsequent transformations, are fascinating tools for the rapid and effective synthesis of molecular scaffolds with potential pharmacological relevance. We became interested in the preparation of novel 5-aroyl-1-aryltetrazoles as (1) they still represent challenging structures not easily accessible through the methods described in literature, and (2) the α-ketotetrazolic framework may be considered as a potential bioisostere of the enonic linker of chalcones. In the present work, a novel, simple, effective and general synthesis for this class of compounds is described.
A formal intramolecular vicinal 1,2-diamination of alkynes is achieved for the synthesis of indole-cyclic urea fused derivatives through a double cyclization process from readily available aminophenyl propargyl alcohols. This sequential triple C–N bond construction event was possible using isocyanate as urea precursor and Ag(I) catalyst as alkyne activating agent. Control experiments reveal that the
silver‐catalyzed chemoselective [4+2] annulation of aryl and heteroaryl isocyanides with α‐substituted isocyanoacetamides was developed for the facile and efficient synthesis of 2‐aminoquinolones, naphthyridines, and phenanthrolines. A mechanism for this multistep domino reaction is proposed on the basis of a 13C‐labeling experiment, according to which an unprecedented chemoselective heterodimerization