REACTION OF ALIPHATIC-AMINES WITH 49-PERCENT FORMIC-ACID - 1-HEXYLAMINE, DI-1-HEXYLAMINE, N,N-DIMETHYL-1-HEXYLAMINE, 1-DODECYLAMINE, N,N-DIMETHYL-1-DODECYLAMINE AND N,N-DIMETHYL-1-BUTYLAMINE

Two primary amines, 1-hexylamine 2, 1-dodecylamine 19, one secondary a mine, di-1-hexylamine 18, and three tertiary amines, N,N-dimethyl-1-he xylamine 6, N,N-dimethyl-1-butylamine 3, and N,N-dimethyl-1-dodecylami ne 22 were each heated at 150 degrees C, 250 degrees C or 350 degrees C with 49% aqueous formic acid for varying periods of time. The alipha tic primary amines underwent easy N-formylation and subsequent reducti on to give N-methyl- and N,N-dimethylalkylamines. Especially at higher temperatures, other reactions intervened including elimination of NH3 to the corresponding alkenes followed by partial double bond isomeriz ation. Tertiary amines were more reactive at higher temperatures under going hydrolysis and reductive cleavages to secondary and primary amin es, which subsequently followed the reaction sequences seen for primar y amines. This series of saturated amines showed none of the cleavage into smaller fragments that was observed in the reductive alkylation o f pyridine and 4-methylpyridine to a series of N-alkylpiperdines. This result reinforces the bis-aza-retro-Aldol-fragmentation mechanism pos tulated for the formation of the N-alkylpiperidines.