Synthesis and structural properties of bridged 1,8-diazacyclotetradeca-4,11-diynes

The synthesis of 1,8-diazacyclotetradeca-4,11-diyne (4) was accomplished by reaction of 1,6-dibromo-3-hexyne (11) with ammonia. Similarly, the prepara tion of 1-azacyclotetradeca-4,11-diyne (5) was achieved from 1,13-dibromotr ideca-3,11-diyne (10) and ammonia. The reaction of alpha,omega-diamines of Linear hydrocarbons of the chain length C-4 to C-10 with 11 yielded the cor responding bicyclic diynes 23-29. The reaction of 4 with II yielded 1,8-dia zabicyclo[6.6.6]icosa-4,11,16-triyne (14). Similarly, the reaction of 4 wit h 1,4-dibromo-2-butyne yielded 1,8-diazabicyclo[6.6.4]octadeca-4,11,16-triy ne (31). The molecular structures of 1,8-are situated in one plane. diisopr opyl-1,8-diazacyclotetradeca-4,11-diyne (13a), as well as of 14, 24, 27 and 31 were studied by means of the X-ray technique. It was found that 13a ado pts a chair-like conformation (C-2h) With an equatorial orientation of the isopropyl groups. In 14, 24, 27, and 31 the 14-membered rings adopt a twist -boat conformation. The distance between the nitrogen atoms varies between 4.662(2) and 5.189(2) Angstrom. In the case of 14, 24 and 27 the nitrogen a toms are pyramidalized and point inside the cage while in 31 the substituen ts at each nitrogen atom and the nitrogen atoms are situated in one plane.