Gold/Lewis acid catalyzed oxidative cyclization involving activation of nitriles

Recent advances in metal carbene-induced semipinacol rearrangements

As has been well-recognized, the semipinacol rearrangements (SPRs) function as a powerful and versatile tool for the construction of all-carbon and heteroatom-containing quaternary stereocenters, which are present in various natural products and bioactive molecules. In recent years, considerable attention has been paid to exploring the metal carbene-induced semipinacol rearrangements, providing an attractive and powerful strategy for obtaining various important carbonyl compounds. However, to date, no review has been published that summarizes the significant advances in the preparation of functionalized carbonyl compounds using these migration rearrangement reactions. In this review article, we have summarised the recent advances in the field of metal carbene-induced SPR reactions according to different metal classifications. Mechanistic insights, synthetic applications, and their limitations are discussed. The challenges and opportunities in this field are also outlined.

Solvent-dependent chemoselective synthesis of different isoquinolinones mediated by the hypervalent iodine(III) reagent PISA

Isoquinolinone is an important heterocyclic framework in natural products and biologically active molecules, and the efficient synthesis of this structural motif has received much attention in recent years. Herein, we report a (phenyliodonio)sulfamate (PISA)-mediated, solvent-dependent synthesis of different isoquinolinone derivatives. The method provides highly chemoselective access to 3- or 4-substituted isoquinolinone derivatives by reacting o-alkenylbenzamide derivatives with PISA in either acetonitrile or wet hexafluoro-2-isopropanol.

Cyclization-Carbonylation of 2-Alkynyl Primary Benzamides using p-Benzoquinone under Neutral Conditions

A palladium-catalyzed cyclization-carbonylation of 2-alkynyl primary benzamides 1 afforded methyl 3-substituted 1-methoxyisoquinoline-4-carboxylates 6 in good to moderate yields. In the case of mesylate 1r, 12 was obtained directly via a cyclization-carbonylation-cyclization cascade. Compounds 6 were converted to isoquinolin-1(2H)-ones 8 in good yields under microwave irradiation. In the case of the mesylate 6q, tricyclic isoquinolinone 10 was obtained in good yield. The reactions of thiophene-2-carboxamide derivatives also proceeded well.

Gold-Catalyzed Oxidative Cyclization/C-C Bond Cleavage of Ynones with External Nucleophiles: Synthesis of Linear Functionalized N-Tosylamides

A gold-catalyzed oxidative cyclization/nucleophilic addition/C-C bond cleavage reaction of ynones with various nucleophiles has been developed. This methodology allows for the formation of highly functionalized linear N-Ts amides with broad substrate scope, high efficiency, and general tolerance of functional groups. A wide range of nucleophiles such as alcohols, water, and amines including aryl and alkyl amines are compatible with the current method. The C-C triple bond cleavage of the ynone substrate was observed during the process.

One-Pot Synthesis of 3-(1,2,3,4-Tetrahydroisoquinolin-1-yl)-isoquinolin-1(2H)-ones by DEAD-Promoted Oxidative Ugi–Wittig ­Reaction Starting from Phosphonium Salt Precursors

A new one-pot synthesis of 3-(1,2,3,4-tetrahydroisoquinolin-1-yl)-isoquinolin-1(2H)-ones by DEAD-promoted oxidative Ugi–­Wittig reaction was developed. The sequential reactions of (2-carboxybenzyl)triphenylphosphonium salts, isocyanides, and N-aryl-1,2,3,4-tetrahydroisoquinolines produced 3-(1,2,3,4-tetrahydroisoquinolin-1-yl)-isoquinolin-1(2H)-ones in moderate to good overall yields in the presence of DEAD and Et3N.

Efficient synthesis of tetracyclic γ-lactams via gold-catalyzed oxidative cyclization of alkenyl diynes

An efficient gold-catalyzed cascade cyclization of alkenyl diynes involving alkyne oxidation, carbene-alkyne metathesis and cyclopropanation has been developed, furnishing a series of tetracyclic γ-lactams bearing one quaternary carbon center and...

Theoretical insights into the mechanism and origin of chemoselectivity in the catalyst- and directing group-dependent oxidative cyclization of diynes with pyridine N-oxides

The mechanisms and origin of the chemoselectivity of Cu(i)- and Au(i)-catalyzed oxidation of diynes for the divergent syntheses of two different N-heterocycles, substituted pyrroles and dihydroindeno[1,2-c]pyrrol-3(2H)-ones, were elucidated using density functional theory.

Gold-Catalyzed Oxidative Cyclization Involving Nucleophilic Attack to the Keto Group of α,α'-Dioxo Gold Carbene and 1,2-Alkynyl Migration: Synthesis of Furan-3-carboxylates

A multicomponent strategy for the synthesis of functionalized furan-3-carboxylates based on gold-catalyzed oxidative cyclization of diynones with alcohols or water has been developed. Mechanistic studies revealed that a rare nucleophilic attack to the carbonyl group of the α,α'-dioxo gold carbene instead of the carbene center and 1,2-alkynyl group migration were involved in this transformation. This method offers several advantages such as mild conditions, high regio- and chemoselectivity, and wide functional group compatibility.