Coupling-Isomerization-N,S-Ketene Acetal-Addition Sequences-A Three-Component Approach to Highly Fluorescent Pyrrolo[2,3-b]pyridines,[1,8]Naphthyridines,and Pyrido[2,3-b]azepines

摘要

Annelated 2-amino pyridines such as pyrrolo[2,3-b]pyridines,[1,8]naphthyridines,and pyrido[2,3-b]-azepines can be synthesized in moderate to good yields in a consecutive one-pot three-component process by a coupling-isomerization-enamine-addition-cyclocondensation sequence of an electron-poor (hetero)-aryl halide,a terminal propargyl N-tosylamine,and an N,S-ketene acetal.After the coupling-isomerization sequence,a Diels-Alder reaction with inverse electron demand of the intermediate enimine and the N,S-ketene.acetal and subsequent aromatization furnish annelated 2-amino pyridines 4 that were unambiguously characterized by numerous X-ray structure analyses.These heterocycles are highly fluorescent and partially pH sensitive,and their electronic structure was studied with spectroscopic and computational methods.