Process Development and Scale-Up of a Benzoxazepine-Containing Kinase Inhibitor

The benzoxazepine core is present in several kinase inhibitors, including the mTOR inhibitor 1. The process development for a scalable synthesis of 7-bromobenzoxazepine and the telescoped synthesis of 1 are reported. Compound 1 consists of three chemically rich, distinct fragments: the tetrahydrobenzof1,4oxazepine core, the aminopyridyl fragment, and the substituted (methylsulfonyl)benzoyl fragment. Routes were developed for the preparation of 3-fluoro-2-methyl-4-(methylsulfonyl)benzoic acid (17) and tert-butyl 7-bromo-2,3-dihydrobenzof1,4oxazepine-4(5H)-carboxylate (2). The processes for the two compounds were scaled up, and over 15 kg of each starting material was prepared in overall yields of 42% and 58%, respectively. A telescoped sequence beginning with compound 2 afforded 7.5 kg of the elaborated intermediate 5-(2,3,4,5-tetrahydrobenzof1,4oxazepin-2-amine dihydrochloride (6) in 63% yield. Subsequent coupling with benzoic acid 17 gave 7.6 kg of the target compound 1 in 84% yield. The preferred hydrochloride salt was eventually prepared. The overall yield for the synthesis of inhibitor 1 was 21% over eight isolated synthetic steps, and the final salt was obtained with 99.7% HPLC purity.