Reduction of imidazolium salts – An approach to diazocines and diazocanes

A convenient approach to diazocine derivatives 8,9 starting from 1,2-polymethyle-neimidazolium salts 4 was developed. The polymethylenimidazolium salts 4 are partially reduced with sodium borohydride in DMF to give 5,6,7,7a-tetrahydro-1H-pyrrolo[1,2-a]imidazoles 5 or under more forcing conditions – (sodium triacetoxyborohydride in acetic acid) with cleavage of the endocyclic C–N bond affording diamines 6. Tertiary salts 7 readily prepared from compounds 5 react with NaBH₄ and KCN nucleophiles with cleavage of the endocyclic N–C bond to form diazocine derivatives 8,9.