Pd-catalyzed oxidative amidation of aldehydes with hydrogen peroxide

Amidation of aldehydes and alcohols through α-iminonitriles and a sequential oxidative three-component Strecker reaction/thio-Michael addition/alumina-promoted hydrolysis process to access β-mercaptoamides from aldehydes, amines, and thiols

Mild and general alumina-promoted hydrolysis conditions for converting α-iminonitriles into carboxamides have been developed. In combination with the oxidative three-component Strecker reaction, the one-pot direct amidation of aldehydes and alcohols is reported. Subsequently, an Yb(OTf)(3)-catalyzed Michael addition of thiols to α,β-unsaturated α-iminonitriles is reported for the synthesis of β-mercapto-α-iminonitriles. The successful integration of an oxidative Strecker reaction, thio-Michael addition, and neutral-alumina-promoted hydrolysis of β-mercapto-α-iminonitriles into a three-component one-pot process allowed us to develop the direct conversion of amines, aldehydes, and thiols into β-mercaptoamides. All of these procedures were applicable to aromatic and aliphatic amines and aldehydes.

Iron(II)-catalyzed amidation of aldehydes with iminoiodinanes at room temperature and under microwave-assisted conditions

A method for the amidation of aldehydes with PhI=NTs/PhI=NNs as the nitrogen source and an inexpensive iron(II) chloride + pyridine as the in situ formed precatalyst under mild conditions at room temperature or microwave assisted conditions is described. The reaction was operationally straightforward and accomplished in moderate to excellent product yields (20-99%) and with complete chemoselectivity with the new C-N bond forming only at the formylic C-H bond in substrates containing other reactive functional groups. By utilizing microwave irradiation, comparable product yields and short reaction times of 1 h could be accomplished. The mechanism is suggested to involve insertion of a putative iron-nitrene/imido group to the formylic C-H bond of the substrate via a H-atom abstraction/radical rebound pathway mediated by the precatalyst [Fe(py)(4)Cl(2)] generated in situ from reaction of FeCl(2) with pyridine.

Metal-catalysed approaches to amide bond formation

Amongst the many ways of constructing the amide bond, there has been a growing interest in the use of metal-catalysed methods for preparing this important functional group. In this tutorial review, highlights of the recent literature have been presented covering the key areas where metal catalysts have been used in amide bond formation. Acids and esters have been used in coupling reactions with amines, but aldehydes and alcohols have also been used in oxidative couplings. The use of nitriles and oximes as starting materials for amide formation are also emerging areas of interest. The use of carbon monoxide in the transition metal catalysed coupling of amines has led to a powerful methodology for amide bond formation and this is complemented by the addition of an aryl or alkenyl group to an amide typically using palladium or copper catalysts.

Dienyl homoallyl alcohols via palladium catalyzed ene-type reaction of aldehydes with 1,3-dienes

The combination of Pd catalyst and Xantphos ligand in the presence of Et(3)B nicely promotes the allylation of aldehydes with conjugated dienes to provide dienyl homoallyl alcohols in excellent yields. The reaction occurs selectively at the C-C double bond bearing higher electron density.

Catalytic acylation of amines with aldehydes or aldoximes

The simple nickel salt NiCl(2)·6H(2)O catalyzes the coupling of aldoximes with amines to give secondary or tertiary amide products. The aldoxime can be prepared in situ from the corresponding aldehyde. The use of (18)O-labeled oximes has allowed insight into the mechanism of this reaction.

Direct amide synthesis from either alcohols or aldehydes with amines: activity of Ru(II) hydride and Ru(0) complexes

An in situ generated catalyst from readily available RuH(2)(PPh(3))(4), an N-heterocyclic carbene (NHC) precursor, NaH, and acetonitrile was developed. The catalyst showed high activity for the amide synthesis directly from either alcohols or aldehydes with amines. When a mixture of an alcohol and an aldehyde was reacted with an amine, both of the corresponding amides were obtained with good yields. Homogeneous Ru(0) complexes such as (eta(4)-1,5-cyclooctadiene)(eta(6)-1,3,5-cyclooctatriene)ruthenium [Ru(cod)(cot)] and Ru(3)(CO)(12) were also active in the amidation of an alcohol or an aldehyde with the help of an in situ generated NHC ligand.

Single-flask synthesis of N-acylated indoles by catalytic dehydrogenative coupling with primary alcohols

Indoles and alcohols can be coupled in a dehydrogenative process catalyzed by tetrapropylammonium perruthenate. This efficient approach to indolylamides proceeds in a single flask under mild conditions. By employing substituted indoles and alkyl, branched, or benzylic alcohols, a variety of indolylamides can be formed. Aryl indolylamides can be functionalized through an additional dehydrogenative coupling to furnish elaborated polycyclic heterocycles similar to biologically active structures previously reported.