Regioselective monometalation of 2,5‐pyridinedicarboxamides with (2,2,6,6‐tetramethylpiperidino)magnesium chloride (TMPMgCI)

Abstract

Abstract The 2,5‐pyridinecarboxamides 9–15 were synthesized in one or two steps from diester 1 by addition of an excess of dimethylaluminium amide or successive addition of two different dimethylaluminium amides with or without intermediate workup. For the carboxamides 16 and 17 this method failed; they were, however, available by other procedures. Metalation of the carboxamides 9–17 with TMPMgCI and subsequent reaction with electrophiles led to the 2,3,5‐ and 2,4,5‐substituted pyridines 9a/b‐17a/b, 18 and 19 with regioselectivities ranging from predominant 4‐substitution to complete 3‐substitution.