Titanocene-catalyzed coupling of aromatic amides in the presence of organosilanes: a novel route to vicinal diamines and a new class of amine-substituted oligomers.
The title reaction has been surveyed for a number of substrates with differing substitution patterns. With a few exceptions, the methodology provides a one-pot synthesis of the 1,2-diamines from widely available and inexpensive starting materials, and in high yields. In addition, the coupling of 1,4- and 1,3-bis-(N,N,N',N'-tetraalkyl)arylenediamides is shown, under the same experimental conditions, to yield oligomers: R2NC(O)C6H4CH(NR2)-[CH(NR2)C6H4CH(NR2)]n-CH(NR2)C6H4C(O)-NR2 (R = methyl and ethyl; n = 0 to ca. 5). The chemical structures of these unprecedented oligomers are determined by comparison of NMR and MS spectra to those of vicinal diamines, prepared from the analogous N,N-dialkylbenzamides. The origin of the limitation of oligomer chain length is probably due to a specific effect of the internal benzylic amine group, since the substrate 4-Me2NCH2C6H4C(O)NMe2 was found to be uniquely unreactive compared to the other 4-substituted N,N-dialkylbenzamides investigated. N-Methylphthalimide was briefly studied as a monomer and analysis by MS showed that oligomers are formed. Attempts to fully characterize these polymers were unsuccessful.
Rangareddy
Kesamreddy
K
Chemistry Department, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada.
Selvakumar
Kumaravel
K
Harrod
John F
JF