Structures of Pyridines Obtained in the Aluminum Bromide Mediated Cyclocongregation of Acetylenes with Cyanoformates

Article abstract of DOI:10.1021/jo00182a004

It is shown that the product of the title reaction with tert-butylacetylene and ethyl cyanoformate is not ethyl 3,5-di-tert-butyl-2-picolinate as reported in the recent literature but rather the 4,5-isomer.Varying yields of the 4,6-isomer are also obtained.The NMR spectra described for the 3,5-dimethyl analogue likewise suggest a misassignment of structure in that case.A revised mechanism is tentatively given for these reactions.