Jbr. Devains et al., NEW SYMMETRICAL AND UNSYMMETRIC POLYFUNCTIONALIZED 2,2'-BIPYRIDINES, Journal of heterocyclic chemistry, 31(4), 1994, pp. 1069-1077
Recently, a large number of biheterocycles have been synthesized in or
der to build macrobicyclic cryptates. To pursue investigations in this
field, we prepared new symmetric and unsymmetric functionalized bipyr
idines and we describe here two synthetic strategies leading to new te
trasubstituted 3 to 15 and trisubstituted 17 to 29 bipyridines. Modifi
cation at the alpha,alpha'-methyl groups and introduction of functiona
lities in the 4,4'-positions have been performed after N-O activation
of the starting 6,6'-dimethyl-2,2'-bipyridine unit. In the case of cya
no and hydroxymethyl groups, alkylation of the N-O function followed b
y a nucleophilic attack with the CN anion or an hydroxymethyl radical
allowed us to obtain the dissymmetric species. To understand observed
differencies between cyanation and hydroxymethylation processes, the u
nstable and hygroscopic N-methoxybipyridinium salt 30 has been isolate
d and characterized by nmr. Dibromomethyl compounds 8, 15, 29 were fin
ally obtained in good to moderate yields by the Boekelheide rearrangem
ent followed by a pseudohalogen exchange.