A Practical, Protecting-Group-Free Synthesis of a PI3K/mTOR Inhibitor

We report a practical and protecting-group-free synthesis amenable to produce multikilogram amounts of PI3K/mTOR inhibitor GDC-0980. The route employed metalation/formylation and reductive amination followed by a metal catalyzed Suzuki–Miyaura cross-coupling. The metalation was performed via triarylmagnesiate intermediates allowing formylation under noncryogenic conditions. 2-Picoline·BH₃ was employed to replace Na­(OAc)₃BH in the reductive amination and to eliminate the use of molecular sieves. A concise one-step synthesis was developed for the selective monoamidation of piperazine with (S)-lactate to produce the piperazine lactamide starting material. The boronic acid was produced from 2-amino-5-bromopyrimidine in a one-step and protecting-group-free approach. The final crystallization in 1-propanol and water afforded the API in 59% overall yield in four steps and >99% purity by HPLC.