1,n-Diamines. Part 2: Synthesis of acyclic and heterocyclic N-arylputrescine derivatives

In the present Letter we report the use of N-arylputrescines as synthetic intermediates for the preparation of N-acyl-N′-aryltetramethylenediamines 3 and related seven-membered heterocyclic amidines 4. Compounds 1 were synthesized by Cs2CO3/KI-mediated aminolysis of 4-chlorobutyronitrile and subsequent reduction. N-Acylation of diamines 1 with carboxylic acid anhydrides led selectively to N-acyl-N′-aryl tetramethylenediamines 3. Microwave-assisted ring closure of such precursors promoted by PPE allowed for the synthesis of hitherto unreported 1-aryl-2-alkyl-1H-1,4,5,6-tetrahydro-1,3-diazepines 4.