Strain control in nucleophilic cyclizations: reversal of <i>exo</i>
-selectivity in cyclizations of hydrazides of acetylenyl carboxylic acids by annealing to a pyrazole scaffold
作者:Sergei F. Vasilevsky、Brian Gold、Tatyana F. Mikhailovskaya、Igor V. Alabugin
DOI:10.1002/poc.2990
日期:2012.11
Independent of the nature of alkyne substitution, hydrazides of 4‐arylethynyl‐5‐carboxylicacidannealed at the pyrazolescaffold undergo a regioselective base‐catalyzed 6‐endo‐dig cyclization with the formation of pyrazolo[3,4‐c]pyridine‐7‐ones. This behavior contrasts the observation of selective 5‐exo closures in the analogous benzannelated systems and illustrates selective destabilization of the