Preparation of 1‐Azacyclododeca‐3,8‐diynes and 1,6‐Diazacyclododeca‐3,8‐diynes

The preparation of N,N′‐dialkyl‐ and N,N′‐diaryl‐1,6‐diazacyclodeca‐3,8‐diynes was achieved by reaction of alkyl‐ or arylamines with 1,4‐dihalobut‐2‐yne under dilution conditions in yields of 5–15%. The compounds synthesized by this procedure were the N,N′‐dimethyl (2b), N,N′‐diethyl (2c), N,N′‐diisopropyl (2d), N,N′‐di‐tert‐butyl (2e), N,N′‐dicyclohexyl (2f), N,N′‐diphenyl (2g), and N,N′‐di‐p‐tolyl (2h) derivatives. The parent compound 2a was obtained in ca. 40% yield by heating 2d with α‐chloroethylchloroformate (20). Using 1,9‐dibromonona‐2,7‐diyne (10) and methylamine or isopropylamine, respectively, the corresponding N‐alkyl‐1‐azacyclodeca‐3,8‐diynes 4b and 4d were synthesized under dilution conditions. By heating 4d with 20 we obtained 1‐azacyclodeca‐3,8‐diyne (4a). As side products of the cyclization reactions the trimers 18 and tetramers 12 and 19 were isolated and characterized. N‐methyl‐1‐azacycloundeca‐3,9‐diyne (14b) was prepared by reaction of 1,10‐dibromodeca‐3,8‐diyne (13) with methylamine.