Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

Intramolecular activation of strong Si-O bonds by gold(I): regioselective synthesis of 3-bromo-2-silylbenzofurans

The high reactivity of gold-vinylidene complexes, generated in situ by [1,2]-bromine shift from the corresponding 1-bromoalkynes, allows the activation of one of the strongest bonds in organic chemistry (Si-O), strategically placed at the ortho-position. In this way, the synthesis of 3-bromo-2-silylbenzofuranes is achieved in good yields. Several substituents with different electronic properties and substitution patterns are well tolerated on the tethering aromatic ring as well as a number of silyl groups on the O-atom. A preliminary mechanistic study is compatible with the participation of gold vinylidene intermediate species. The synthetic applicability of the obtained scaffolds was preliminarily showcased by orthogonal C-C bond forming transformations.

Gold-Catalyzed Hydroarylation Reactions: A Comprehensive Overview

The hydroarylation of alkynes, alkene, and, allene is a cost-effective and efficient way to incorporate unsaturated moieties into aromatic substrates. This review focuses on gold-catalyzed hydroarylation, which produces aromatic alkenes,...

TfOH catalysed domino-double annulation of arenes with propargylic alcohols: a unified approach to indene polycyclic systems

The design and development of a TfOH catalysed domino strategy for the double annulation of arenes with propargylic alcohols for the rapid generation of indene based polycyclic systems is reported. The dehydration, intramolecular 6-endo-dig hydroarylation, and cationic cyclization were consecutively promoted by TfOH. The key features of this strategy are the formation of two C-C bonds, unified access to indene polycyclic systems, excellent yields (up to 95%), high atom economy (>90%), an operationally simple procedure, and water being the only byproduct. By extending this strategy, a two-step synthesis of the pentacyclic systems of hypoxylonol A (43% overall yield from α-tetralone), daldinone A (63% overall yield from β-tetralone) and spiro-tetracyclic framework of incarviatone A has also been achieved.

From Propargylic Alcohols to Substituted Thiochromenes: gem-Disubstituent Effect in Intramolecular Alkyne Iodo/hydroarylation

This work describes the 6-endo-dig cyclization of S-aryl propargyl sulfides to afford 2H-thiochromenes. The substitution at the propargylic position plays a crucial role in allowing intramolecular silver-catalyzed alkyne hydroarylation and N-iodosuccinimide-promoted iodoarylation. Additionally, a PTSA-catalyzed thiolation reaction of propargylic alcohols was developed to synthesize the required tertiary S-aryl propargyl ethers. The applicability of merging these two methods is demonstrated by synthesizing the retinoic acid receptor antagonist AGN194310.

Transition Metal Vinylidene- and Allenylidene-Mediated Catalysis in Organic Synthesis

With their mechanistic novelty and various modalities of reactivity, transition metal unsaturated carbene (alkenylidene) complexes have emerged as versatile intermediates for new reaction discovery. In particular, the past decade has witnessed remarkable advances in the chemistry of metal vinylidenes and allenylidenes, leading to the evolution of a diverse array of new catalytic transformations that are mechanistically distinct from those developed in the previous two decades. This review aims to provide a survey of the recent achievements in the development of organic reactions that make use of transition metal alkenylidenes as catalytic intermediates and their applications to organic synthesis.

In(III)-TMSBr-Catalyzed Cascade Reaction of Diarylalkynes with Acrylates for the Synthesis of Aryldihydronaphthalene Derivatives

A combined Lewis acid system comprising of two or more Lewis acids occasionally exhibits augmented catalytic activity in organic transformations which are otherwise unrealizable by either of the components exclusively. On the other hand, the efficient construction of multiple new C-C bonds and polycyclic structures in minimal steps remains a subject of great interest in both academia and industry. Herein we report an efficient method to assemble aryldihydronaphthalene derivatives via a cascade reaction of diarylalkynes with acrylates under the catalysis of a combined Lewis acid derived from In(III) salt and TMSBr.

Sequential In-catalyzed intramolecular hydroarylation and Pd-catalyzed cross-coupling reactions using bromopropargyl aryl ethers and amines

A sequential one-pot In-catalyzed intramolecular hydroarylation and Pd-catalyzed cross-coupling reaction using bromopropargyl aryl ethers and amines has been developed.

Synthesis of Allylic Amide Functionalized 2H-Chromenes and Coumarins Using a One-Pot Overman Rearrangement and Gold(I)-Catalyzed Hydroarylation

A four-step synthesis of allylic trichloroacetimidates bearing a 2-proparyloxyaryl group has been developed from readily available 2-hydroxybenzaldehydes, and these have been used for the preparation of allylic amide derived 2H-chromenes using an Overman rearrangement and a 6-endo-dig hydroarylation. High yields of the 2H-chromenes were achieved using a stepwise approach involving an Overman rearrangement under thermal conditions followed by a hydroarylation reaction with a gold(I) triflimide catalyst. An alternative method where both reactions were performed as a one-pot process was also developed and instead used a gold(I) chloride catalyst activated by silver(I) hexafluoroantimonate for the cycloisomerization step. The allylic amide derived 2H-chromenes were converted to the corresponding coumarin analogues by a pyridinium dichromate (PDC)-mediated chemoselective allylic oxidation.

Gold(i)-catalyzed intramolecular hydroarylation and the subsequent ring enlargement of methylenecyclopropanes to cyclobutenes

Gold(i)-catalyzed intramolecular hydroarylation and the ring enlargement of methylenecyclopropanes containing aryl propargyl ether to give 2H-chromene derivatives and the corresponding cyclobutenes.

Gold-Catalyzed Ring Expansion of Alkynyl Heterocycles through 1,2-Migration of an Endocyclic Carbon-Heteroatom Bond

A mild and efficient gold-catalyzed oxidative ring-expansion of a series of alkynyl heterocycles using pyridine-N-oxide as the oxidant has been developed, which affords highly valuable six- or seven-membered heterocycles with wide functional group toleration. The reaction consists of a regioselective oxidation and a chemoselective migration of an endocyclic carbon-heteroatom bond (favored over C-H migration) with the order of migratory aptitude for carbon-heteroatom bonds being C-S>C-N>C-O. In the absence of an oxidant, polycyclic products are readily constructed through a ring-expansion/Nazarov cyclization reaction sequence.

Indium-catalyzed intramolecular hydroarylation of aryl propargyl ethers

Indium(iii) halides are efficient and selective catalysts for the intramolecular hydroarylation of aryl propargyl ethers.