Reductive mono- and diallylation of the bis(pyridine)dihydropyridyllithiumdimer by triallylborane

Reductive allylation of the bis(pyridine)dihydropyridyllithium dimer contai ning the 1,2- and 1,4-dihydropyridine fragments by triallylborane results m ainly in trans- and cis-2,6-diallyl-piperidines (60-85%), their ratio depen ding on the nature of the solvent. The minor reactions products are 2-allyl -1,2,3,6-tetrahydropyridine and 4,10-diallyl-3,9-diazatricyclo[6.2.2.0(2.7) ]dodecane. The unexpected formation of the latter is due to hetero-Diels-Al der condensation of intermediate products formed in the allylboration of di hydropyridines. The stereochemistry of trans- and cis-2,6-diallylpiperidine s was determined from the H-1 and C-13 NMR spectra of the respective N,N-di methylpiperidinium iodides. The structure of 4,10-diallyl-3,9-diazatricyclo [6.2.2.0(2.7)]dodecane dipicrate was established by X-ray diffraction analy sis.