A General Route to 1,3′-Bipyrroles

A general method is described for
the synthesis of 1,3′-bipyrroles.
The route involves constructing a pyrrole ring on the nitrogen of
a substituted 1H-pyrrole, so as to generate the 1,3′-bipyrrole.
In this approach the nitrogen of the starting pyrrole was alkylated
with a special Michael acceptor having an allylic leaving group, and
the product was then modified in such a way that the second pyrrole
ring could be formed by a Paal–Knorr reaction. Two variants
of this sequence were examined, one of which led to formation of a
3-hydroxypyridine instead of the second pyrrole ring; the other variant
used phenacyl bromide instead of the special Michael acceptor.