Development of a Manufacturing Process for 1-(1-Pyridin-2-yl methyl-piperidin-4-yl)-1H-indole:  A Key Intermediate for Protein Kinase C Inhibitor LY317615

This contribution describes process development leading to the production of 1-(1-pyridin-2-yl methyl-piperidin-4-yl)-1H-indole (11). The title compound 11 was produced via a Leimgruber−Batcho indole synthesis using key intermediates 2-(2,2-dimethoxyethyl)benzenamine (6) and, 1-(2-pyridinylmethyl)-4-piperidinone camphor sulfonate (9). Direct crystallization of 11 from IPA or ethanol−water was developed to provide (11) with <1% impurities and high yield (78%). The combined process leads to a five-step synthesis of 11 that was efficient and reflected Eli Lilly and Company's commitment to implementation of environmental friendly processes whenever feasible.