Deuteration and tautomeric reactivity of the 1-methyl functionality of free-base dipyrrins

Org Biomol Chem. 2017 Sep 26;15(37):7925-7935. doi: 10.1039/c7ob01278k.

Abstract

Regioselective reactivity of the 1-methyl group of free-base dipyrrins is explored, including discussion of tautomerism to provide exocyclic alkenyl reactivity. Deuterium is installed so as to generate dipyrrins substituted with deuterated methyl groups. Furthermore, the 1-methyl group reacts to become involved in C-C bonds involving only sp3-hybridised carbon atoms. The isolation of an elusive framework featuring a dipyrrin substituted with a pyrrole in a non-vinylogous fashion is also reported. The use of asymmetric dipyrrins featuring an electron-withdrawing group on one of the pyrrolic units results in regioselective reaction of the alpha-methyl group distal to the electron-withdrawing group.