Arene chromium tricarbonyl complexes in synthesis
The last chapter describes an extension of this cyclisation reaction enabling the synthesis of homochiral l-aryl-l,2,4,5-tetrahydrobenzazepines. The stereoselectivity observed in the acid-mediated cyclisation of homochiral N-(3,4-dimethoxyphenethyl)halostachine to Nmethyl- l-phenyl-l,2,4,5-tetrahydrobenzazepine is assessed. The chromium tricarbonyl complex of this cyclisation precursor undergoes a stereoselective cyclisation to furnish the homochiral 1-aryl benzazepine after decomplexation. The diastereoselectivity observed in the acid-mediated cyclisation of homochiral N-3,4-dimethoxyphenethyl phenylpropanolamines is also investigated and the mechanism by which they occur is discussed. Coordination of one of these precursors to the chromium tricarbonyl unit renders the cyclisation stereoselective to give homochiral N-methyl-1 -phenyl-2-methyl-7,8-dimethoxy-1,2,4,5-tetrahydrobenzazepine after decomplexation.