REGIOSELECTIVE MONOMETALATION OF 2,5-PYRIDINEDICARBOXAMIDES WITH (2,2,6,6-TETRAMETHYLPIPERIDINO)MAGNESIUM CHLORIDE (TMPMGCL)

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 meth od failed; they were, however, available by other procedures. Metalati on of the carboxamides 9-17 with TMPMgCl and subsequent reaction with electrophiles led to the 2,3,5- and 2,4,5-substituted pyridines 9ab-17 a/b, 18 and 19 with regioselectivities ranging from predominant 4-subs titution to complete 3-substitution.