ON THE SI-N-BOND - XLV. 2-AZA-ALLENIUM CATIONS: SYNTHESIS, MOLECULAR STRUCTURE AND ELECTROPHILIC RING CLOSURE TO 1H-ISOINDOLES

Article abstract of DOI:10.1016/S0040-4020(01)86833-2

A new synthesis of 2-aza-allenium salts is described starting from N-trimethylsilylimines of aromatic ketones.Molecular structures and charge distributions of the linear allenoid and the angular allylic forms of monosubstituted 2-aza-allenium cations are calculated by the semiempirical MINDO/3 method.The u.v. spectra of tetraaryl-2-aza-allenium cations have been measured and interpreted by theoretical transition energies obtained from modified PPP investigations.The theoretical heats of formation suggest the linear allenoid structure of all these cations to be favoured.Low energy differences between the linear and the angular geometrics as well as the high positive charge at the carbon atoms of the C-N-C systems may explain the electrophilic ring closure to 1-H-isoindoles found experimentally.