Sequential Addition of Amines to Nitrile and Carbon-Carbon Multiple Bond: A Route to 7-Amino-5H-dibenzo[c,e]azepines

A rare earth metal-catalyzed sequential inter- and intramolecular C-N bond formation of 2-nitrile-2'-alkenyl(alkynyl)biphenyls with amines has been developed, which provides a straightforward and efficient access to a range of new functional dibenzo[c,e]azepines. This represents the first examples of direct construction of seven-membered azaheterocycle from unsaturated nitriles and amines. Such transformations have the advantages of avoiding the use of additives, easily available starting materials, step- and high atom-economy, mild reaction conditions, and high selectivity.

Short and Modular Synthesis of Substituted 2-Aminopyrroles

We herein describe a simple and metal-free domino methodology to synthesize 2-aminopyrroles from alkynyl vinyl hydrazides. The domino reaction involves a novel propargylic 3,4-diaza-Cope rearrangement and a tandem isomerization/5-exo-dig N-cyclization reaction. By using this approach, a number of 2-aminopyrroles with diverse substituents have been prepared.

Gold/Lewis acid catalyzed oxidative cyclization involving activation of nitriles

A gold-catalyzed oxidative cyclization of alkyne-nitriles using water or alcohol as the external nucleophiles has been developed. The catalytic system, featured with gold and Lewis acid dual catalysis, allows a facile synthesis of functionalized isoquinolin-1(2H)-ones and 1-alkoxy-isoquinolines with a wide structural diversity.

A minireview of hydroamination catalysis: alkene and alkyne substrate selective, metal complex design

Organic compounds that contain nitrogen are very important intermediates in pharmaceutical and chemical industry. Hydroamination is the reaction that can form C-N bond with high atom economy. The research progress in metals catalyzed hydroamination of alkenes and alkynes from the perspective of reaction mechanism is categorized and summarized.

Hetero-bimetallic cooperative catalysis for the synthesis of heteroarenes

Review covering the synthesis of 5- and 6-membered as well as condensed heteroarenes, focussing on the combinations in cooperative catalytic systems in strategies used to achieve selectivity and also highlights the mode of action for the cooperative catalysis leading to the synthesis of commercially and biologically relevant heteroarenes.

The roles of Lewis acidic additives in organotransition metal catalysis

We present recent advances in prominent organotransition metal-catalysed reactions in which Lewis acid cocatalysts are employed to increase catalyst activity or selectivity. The roles of Lewis acids are discussed.

Lanthanide-Catalyzed Tandem Insertion of Secondary Amines with 2-Alkynylbenzonitriles: Synthesis of Aminoisoindoles

A lanthanide-catalyzed intermolecular hydroamination of 2-alkynylbenzonitriles with secondary amines has been disclosed, providing a streamlined access to a range of aminoisoindoles in moderate to excellent yields. The salient features of this reaction include high bond-formation efficiency, mild reaction conditions, 100 % atomic efficiency and good functional group tolerance. This methodology has also been successfully applied to the construction of other nitrogen-containing compounds, such as 5 H-imidazo[2,1-a]isoindoles and isoquinolines. A plausible mechanism for the formation of aminoisoindoles involving initial N-H activation by a lanthanide complex followed by C≡N insertion into a Ln-N bond to form an amidinate lanthanide intermediate, which undergoes the cyclization is proposed.

Gold-catalysed glycosylation reaction using an easily accessible leaving group

Gold(III)-catalysed glycosylation reaction has been developed by employing a new and easily accessible leaving group synthesized from ethyl cyanoacetate. Several nucleophiles like alcohols, thiols, allyltrimethylsilane, trimethylsilyl azide and triethylsilane have been reacted to make the corresponding glycosides in good yields and with marginal to excellent α-selectivity.

Silver-free two-component approach in gold catalysis: activation of [LAuCl] complexes with derivatives of copper, zinc, indium, bismuth, and other Lewis acids

Complexes of type [LAuCl] (L = phosphine, phosphite, NHC and others) are widely employed in homogeneous catalysis, however, they are usually inactive as such and must be used jointly with a halide scavenger. To date, this role has mostly been entrusted to silver salts (AgSbF6 , AgPF6, AgBF4, AgOTf, etc.). However, silver salts can be the source of deactivation processes or side reactions, so it is sometimes advisable to use silver-free cationic gold complexes, which can be difficult to synthesize and to handle compared with the more robust chloride. We show in this study that various Lewis acids of the transition and main group metal families are expedient substitutes to silver salts. We have tested Cu(I), Cu(II), Zn(II), In(III), Si(IV), Bi(III), and other salts in a variety of typical Au(I)-catalyzed transformations, and the results have revealed that [LAuCl] can form active species in their presence.

Synthesis of spiroaminals by bimetallic Au/Sc relay catalysis: TMS as a traceless controlling group

An efficient synthesis of spiroaminals over fused aminals has been successfully developed by bimetallic Au/Sc catalysis by using TMS as a traceless controlling group.

Combining Zn Ion Catalysis with Homogeneous Gold Catalysis: An Efficient Annulation Approach to N-Protected Indoles

The Fischer indole synthesis is perhaps the most powerful method for indole preparation, but it often suffers from low regioselectivities with unsymmetric aliphatic ketone substrates and strong acidic conditions and is not suitable for α,β-unsaturated ketones. In this article, we disclose an efficient synthesis of N-protected indoles from N-arylhydroxamic acids/N-aryl-N-hydroxycarbamates and a variety of alkynes via a cooperative gold and zinc catalysis. The zinc catalysis is similar to the related zinc ion catalysis in metalloenzymes such as human carbonic anhydrase II and substantially enhances the O-nucleophilicity of N-acylated hydroxamines by forming the corresponding Zn chelates. The Zn chelates can attack gold-activated alkynes to form O-alkenyl-N-arylhydroxamates, which can undergo facile 3,3-sigmatropic rearrangements and subsequent cyclodehydrations to yield N-protected indole products. This new chemistry offers several important improvements over the Fischer indole synthesis: a) the reaction conditions are mildly acidic and can tolerate sensitive groups such as Boc; b) broader substrate scopes including substrates with pendant carbonyl groups (reactive in the Fischer chemistry) and alkyl chlorides (e.g., 3f); c) better regioselectivities for the formation of 2-substituted indoles under much milder conditions; d) 2-alkenylindoles can be prepared readily in good to excellent yields, but the Fischer chemistry could not; e) with internal alkynes both steric and electronic controls are available for achieving good regioselectivities, while the Fischer chemistry is in general problematic.

Gold catalyzed stereoselective tandem hydroamination-formal aza-Diels-Alder reaction of propargylic amino esters

A gold-catalyzed tandem intramolecular hydroamination-formal aza-Diels-Alder reaction of propargylic amino esters is described. The overall process leads to the formation of a tetracyclic framework as a single diastereoisomer, with the creation of four bonds and five stereocenters.

A one-pot catalysis: the strategic classification with some recent examples

In this "Emerging Area", the strategic classification of one-pot catalysis, i.e. cooperative, relay and sequential catalysis, is described. In order to illustrate this classification, we take the readers through a series of recent examples which utilize either metal-metal, metal-organo and organo-organo catalysts. The compilation clearly demonstrates the explosive growth and power of this field, which has become, in the last few years, an important technique particularly in the case of enantioselective catalysis.