A mixture of 1-benzyl-3-piperidinecarbonyl chloride hydrochloride (12.5 g, 45.6 mmol), 10,11-dihydro-5H-dibenz[b,f]azepine (8.9 g, 45.6 mmol), N,N-dimethylaniline (15 ml) and toluene (100 ml) was heated at reflux temperature for 14 h. The mixture was decanted and to the remaining solid 10% ammonia (100 ml) and chloroform (100 ml) were added. The phases were separated and the combined toluene and chloroform phases were dried (K2CO3) and evaporated in vacuo. The residue was purified by gradient chromatography on silica gel (200 g) using benzene and chloroform as eluents. The chloroform fractions afforded the crude product. This was dissolved in ethanol (30 ml) and neutralised with oxalic acid in acetone, affording 8.8 g (39%) of 3-(10,11-dihydro-5H-dibenz[b,f]azepin-5-ylcarbonyl)-1-benzylpiperidine hydrogen oxalate hemihydrate.
