sp<sup>3</sup> C–H Bond Activation with Ruthenium(II) Catalysts and C(3)-Alkylation of Cyclic Amines
作者:Basker Sundararaju、Mathieu Achard、Gangavaram V. M. Sharma、Christian Bruneau
DOI:10.1021/ja203875d
日期:2011.7.13
A selective C(3)-alkylation via activation/functionalization of sp(3) C-H bond of saturated cyclicamines was promoted by (arene)ruthenium(II) complexes featuring a bidentate phosphino-sulfonate ligand upon reaction with aldehydes. This highly regioselective sustainable transformation takes place via initial dehydrogenation of cyclicamines and hydrogenautotransferprocesses.
Reactions of pyrrolidine with 2 equiv of aldehydes without any catalyst in a pressurized vessel at 140–200 °C yielded 1,3-disubstituted pyrroles. α-Branched aldehydes gave fairly good yields of the corresponding products by this method, which provides a facile non-oxidative procedure for synthesizing 1,3-dialkylpyrroles from inexpensive pyrrolidine and aldehydes.
Cyclicamines such as pyrrolidine and piperidine are known to undergo condensations with aldehydes to furnish pyrrole and pyridine derivatives, respectively. A combined experimental and computational study provides detailed insights into the mechanism of pyrrole formation. A number of reactive intermediates (e.g., azomethine ylides, conjugated azomethine ylides, enamines) were intercepted, outlining
1,3-Disubstituted pyrroles were prepared by a microwave-assisted reaction of pyrrolidine and aldehydes in toluene as well as in solvent-free conditions. Reactions were completed in a few minutes in the solvent-free condition but a long time (up to 30min) was necessary to complete reactions in toluene. Yields of products depended considerably on the aldehyde used.