Synthesis of cyclic amines and their alkyl derivatives from amino alcohols over supported copper catalysts

Abstract

Cyclization of amino alcohols over copper supported on γ-alumina and magnesia was found to be an efficient method for the synthesis of cyclic amines, their alkyl derivatives and in some instances also their dehydro derivatives. Reactions were carried out in the temperature range 200–300°C using a continuous fixed-bed reactor and methanol or ethanol as solvent. The selectivities with respect to the different products depended markedly on the reaction temperature and the catalyst used. The amino alcohols used as reactants were 3-amino-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol and 6-amino-1-hexanol. The reaction of 3-amino-1-propanol was unspecific and led to various fragmentation products. In contrast, the reaction of 4-amino- 1-butanol yielded either pyrrolidine (selectivity 62%), N-methylpyrrolidine (71%) or Δ 1-dehydropyrrolidine (47%), depending on the conditions. The reaction of 5-amino-1-pentanol led either to piperidine (99%) or N-methylpiperidine (93%). Hexahydro-1 H-azepine (95%) was the main product of the cyclization of 6-amino-1-hexanol.