CHEMOSELECTIVITY AND STEREOSELECTIVITY IN THE CONDENSATION-REACTIONS OF 4,4'-DIETHYL-2,2'-PERHYDROBIPYRIMIDINE

Rac 1,3-pentanediamine reacts with glyoxal to give a 1:1 mixture of di astereomers from which can be isolated ,4S,4'R*)-4,4'-diethylperhydro -2,2'-bipyrimidine. Subsequent treatment with HCHO, MeCHO, EtCHO, and i-PrCHO gives cis and to a lesser extent trans fused 1:1 condensation products, which are cis-3,6-diethylperhydro-4,5,8a,9a-tetraazafluorene and ans-1,6-diethylperhydro-4,5,8a,9a-tetraazafluorene derivatives, o r tetracyclic cis fused 1:2 condensation products, hylperhydro-3a,4a,7 a,8a-tetraazacyclopentano[def]- fluorenes, respectively, depending on conditions. 2-Phenylacetaldehyde reacts to give cis and trans 2-benzyl -4-ethylhexahydropyrimidine. The effects of aldehyde and solvent upon the outcome are discussed. (C) 1998 Elsevier Science Ltd. All rights r eserved.