摘要:
                                The synthesis and characterization of some (o-formylphenyl)ethylamines are described.  Formylation with DMF of regioselectively lithiated N,N-dimethyl-alpha-(m-methoxyphenyl)ethylamine (1) has provided a route to an unusual ring-chain tautomeric system in which the ring has the dihydroisoindolium structure.  The ring tautomers, with two chiral centers, consist of unequal amounts of two racemates, which undergo rapid, base-catalyzed interconversion at ambient temperature on the 360-MHz NMR time scale.  The geometry and relative energies of the diastereomeric ring structures were estimated from MMP2 calculations.  The trans dihydroisoindolium 3,5-dinitrobenzoate (4d) was characterized by X-ray diffraction, and its geometry was compared with that predicted by calculation.  From NMR experiments with the simpler amino aldehyde 6, it has been concluded that, although a methoxy or hydroxy substituent ortho to the formyl group is not a structural requirement for ring tautomerism, it serves to favor the ring over the chain tautomer.  The (o-formylphenyl)ethyl sulfides 8 and 9, obtained by nucleophilic displacement of the methiodides, show no propensity for ring formation.