Tandem Hydroaminomethylation Reaction to Synthesize Amines from Alkenes

Abstract

In the context of atom economy and low environmental impact, synthesis of amines by an efficient catalytic process is of great importance to produce these building blocks for fine chemical industry. The one-pot hydroaminomethylation of alkenes is a tandem reaction which involves three successive steps under CO/H pressure to perform the catalyzed hydroformylation of the alkene into the corresponding aldehyde followed by its condensation with a N-H function and the catalyzed hydrogenation of the imine/enamine intermediate into the corresponding saturated amine. Rhodium and more recently ruthenium complexes have been designed to combine high conversions of the reactants and chemoselectivity in the expected amines with high regioselectivity in either the linear or the branched amine. The coordination sphere of the metal according to the presence of ligands, temperature, CO/H partial pressures, and nature of the solvent is essential for complying with these selectivity requirements. The rate of the hydroformylation step needs to be fast with regard to the hydrogenation step. The role of amines in the coordination sphere and water, presumably in the second sphere, on the mechanism requires some more studies. Similarly, the enantioselective synthesis of amine is not yet achieved directly and interrupted processes or use of asymmetric organo-catalyzed reductive amination are efficient synthetic ways for producing chiral amines. The separation of the catalyst from the organic products by biphasic or (semi-) heterogeneized systems and its recycling have been demonstrated in many cases. The present review provides a report of the state of the art in this autotandem hydroaminomethylation catalysis and should open prospects in the design of less expensive and abundant metal complexes for reaching at low cost similar and even superior performances.

A General Acid‐Mediated Hydroaminomethylation of Unactivated Alkenes and Alkynes

“…[3] Traditional methods to effect net hydroaminomethylation involve the two-step sequence of alkene hydroformylation followed by reductive amination (Scheme 1, A). [4] More recently,s everal metal-catalyzed direct hydroaminoalkylation reactions of alkenes have been reported that employ simple alkylamines as the starting materials (Scheme 1, B). [5] These approaches,d ominated by early transition-metal catalysts,have shown some restrictions, in part as aconsequence of the thermodynamically challenging CÀHa ctivation step a to secondary amines and of the traditional incompatibility of early transition metals with oxygen functional groups (with only few notable exceptions [5a,b] ).…”

Highly Efficient Construction of Pentacyclic Carboline‐Containing Salts via a [Cp*RhCl2]2‐Catalyzed Tandem Reaction

“…[7] It has stood and out from a number of synthetic strategies and become an important tool for the highly efficient synthesis of complicated cyclic compounds, especially polycyclic compounds with molecular complexity and structural diversity. [7] It has stood and out from a number of synthetic strategies and become an important tool for the highly efficient synthesis of complicated cyclic compounds, especially polycyclic compounds with molecular complexity and structural diversity.…”

Asymmetric Hydrocyanation of Alkenes without HCN

“…[11] Owing to the various transformation of the aldehyde group,h ydroformylation-initiated tandem reactions towards more complex molecules have been achieved, including hydroaminomethylation, [12] hydroformylation/Fischer indole synthesis, [13] hydroformylation/Wittig reaction, [14] and other tandem processes. [11] Owing to the various transformation of the aldehyde group,h ydroformylation-initiated tandem reactions towards more complex molecules have been achieved, including hydroaminomethylation, [12] hydroformylation/Fischer indole synthesis, [13] hydroformylation/Wittig reaction, [14] and other tandem processes.…”

“…Rhodium-catalyzed hydroformylation of alkenes represents ah ighly efficient route for the preparation of aldehydes. [11] Owing to the various transformation of the aldehyde group,h ydroformylation-initiated tandem reactions towards more complex molecules have been achieved, including hydroaminomethylation, [12] hydroformylation/Fischer indole synthesis, [13] hydroformylation/Wittig reaction, [14] and other tandem processes. [15] By contrast, asymmetric hydroformyla-tion-triggered cascade reactions have been rarely reported, although intensive research efforts and much progress have been made in asymmetric hydroformylation during the past decades.…”