A Scalable Synthesis of (R)-3,5-Dihydro-4H-dinaphth[2,1-c:1‘2‘-e]azepine

Environmentally benign scalable procedures are developed to supply enantiomerically pure (R)-3,5-dihydro-4H-dinaphth[2,1-c:1'2'-e]azepine 1 as its hydrogen oxalate salt in a five-step overall yield of 41%, which consist of the following: (1) bis O-triflation of (R)-1,1'-bi-2-naphthol 8 [(CF3SO2)2O, pyridine, PhMe; quantitative yield]; (2) Kumada's cross-coupling [MeMgI, NiCl2(dppp), tert-BuOMe; 96% yield]; (3) radical bromination [N-bromosuccinimide, 2,2'-azobisisobutyronitrile, cyclohexane; 54% yield]; (4) cyclization [allylamine, Et3N, THF, 86%]; (5) N-deallylation [1,3-dimethylbarbituric acid, Pd(OAc)2, Ph3P, PhMe] followed by crystalline salt formation with oxalic acid (overall 92% yield).