Herein,
we report a simple, phosphine-free, and inexpensive catalytic
system based on a manganese(II) complex for synthesizing different
important N-heterocycles such as quinolines, pyrroles, and pyridines
from amino alcohols and ketones. Several control experiments, kinetic
studies, and DFT calculations were carried out to support the plausible
reaction mechanism. We also detected two potential intermediates in
the catalytic cycle using ESI-MS analysis. Based on these studies,
a metal–ligand cooperative mechanism was proposed.
The reductive amination of aromatic aldehydes and aromatic amines, performed in the Brønsted acidic ionic liquid [Et3NH][HSO4], using sodium borohydride as a reducing agent is reported. In this protocol, the ionic liquid plays a crucial role in efficiently converting aromatic aldehydes to amines in excellent yields, without the formation of side products. In the presence of [Et3NH][HSO4], the imine was generated in situ from the reaction between the aromatic aldehydes and aromatic amines, and underwent smooth reduction with sodium borohydride. This one‐pot synthesis is practically simple and sustainable. The catalyst [Et3NH][HSO4] also has a demonstrably wide applicability, in that it can be used with a variety of aromatic aldehydes and aromatic amines substituted by various electron‐withdrawing and electron‐donating groups. The role of IL [Et3NH][HSO4] in catalytic reductive amination is validated with the help of density functional theory (DFT)‐based computational studies.
The selective C7‐allylation of indolines with allyl bromide under ruthenium catalysis has been revealed here. Under established reaction conditions, C7‐allylation of various indolines, including drug compounds, was accomplished with good selectivity and yields. Based on combined experimental and density functional theory (DFT) studies, the olefin insertion route was energetically favorable among four possible pathways. Experimental and DFT studies further revealed that the C−H activation is a reversible rate‐limiting step.
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