Abstract
2-Aminomethylene and 2-hydrazono derivatives 1–6 of carbocyclic and heterocyclic 1,3-dicarbonyl compounds which may form up to four rotational diastereoisomers were investigated by 1H and 13C NMR spectroscopy. The isomeric compositions of the crystalline compounds can be deduced from the 1H signals of equilibrating solutions. Free enthalpies of activation for rotation about the CN and CC bonds of ...
Abstract
2-Aminomethylene and 2-hydrazono derivatives 1–6 of carbocyclic and heterocyclic 1,3-dicarbonyl compounds which may form up to four rotational diastereoisomers were investigated by 1H and 13C NMR spectroscopy. The isomeric compositions of the crystalline compounds can be deduced from the 1H signals of equilibrating solutions. Free enthalpies of activation for rotation about the CN and CC bonds of the enamines and about the NN and CN bonds in the hydrazones were determined by line broadening measurements (Tables 4, 5, and 6). These findings were compared with the results (Table 4) of equilibrations of CN rotamers of enamines which were obtained by separation or enrichment at a preparative scale. Electronic and steric contributions to the rotational barriers are discussed.
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