Molybdenum-Promoted Synthesis of Isoquinuclidines with Bridgehead CF3 Groups.

The preparation of the complex MoTp(NO)(DMAP)(4,5-η2-(2-trifluoromethyl)pyridine) (DMAP = 4-(dimethylamino)pyridine; Tp = tris(pyrazolyl)borate) is described. The CF3 substituent is found to preclude κ-N coordination, allowing for direct coordination without protection of the nitrogen. The dihapto-coordinate complex can be isolated as a single diastereomer, methylated, and reacted with a range of nucleophiles. Oxidative decomplexation affords the free dihydropyridines in good yield (75-90%). As a demonstration of synthetic utility, a series of novel bridgehead CF3-substituted isoquinuclidines was prepared from these decomplexed dihydropyridines.