2,3-Dichloropyridine N-oxide, a novel oxygen transfer reagent, allows the conductance of the gold­(I)-catalyzed oxidation of alkynes to 1,2-dicarbonyls in the absence of any acid additives and under mild conditions to furnish the target species, including those derivatized by highly acid-sensitive groups. The developed strategy is effective for a wide range of alkyne substrates such as terminal- and internal alkynes, ynamides, alkynyl ethers/thioethers, and even unsubstituted acetylene (40 examples; yields up to 99%). The oxidation was successfully integrated into the trapping of reactive dicarbonyls by one-pot heterocyclization and into the synthesis of six-membered azaheterocycles. This synthetic acid-free route was also successfully applied for the total synthesis of a natural 1,2-diketone.

Internal alkynes have been shown to undergo oxidation to substituted benzils (1,2‐diarylethane‐1,2‐diones) by α‐picoline N‐oxide in the presence of Ph3PAuNТf2 (5 mol‐%). In addition to the unsubstituted benzil, the method allows preparing, under markedly mild conditions (50 °C in chlorobenzene), various non‐symmetrical products, including heteroaromatic versions thereof which are much more difficult to obtain otherwise. This gold(I)‐catalyzed transformation was integrated into one‐pot reaction sequence delivering a range of 5‐ to 7‐membered ring systems (imidazoles, quinoxalines, 1,2,4‐triazines, pyrazines, and 1,4‐diazepines), thus linking these important heterocyclic motifs to the internal alkyne reagent space.

Three‐component [2+2+1] gold(I)‐catalyzed reaction of internal alkynes (alkynyl esters or ‐ketones), nitriles, and 2‐chloropyridine N‐oxide led to a wide range of fully substituted 1,3‐oxazoles (32 examples; up to 92% isolated yields). Nitrile R3CN species, employed in the reaction as both reactants and solvents, comprise conventional nitriles (R3=Alk, Ar) and also push‐pull systems such as cyanamides (R3=NH2 and NAlk2) and the thiocyanate (R3=SPr). The advantages of the developed method include mild reaction conditions, high functional‐group tolerance, broad range of substituents R1/R3 along with a possibility of easy modification of COR2 or the amino group when R1=NH2.magnified image

By performing combined XRD and theoretical studies, we established the modes of REWGI⋯I–Pt XBs with [Pt2(μ-I)2I4]2− acting as an XB acceptor.

Gold(I)-catalyzed highly regioselective hydration of alkynylsulfones comprises an efficient 100% atom-economic route to β-ketosulfones. The reaction proceeds under mild mercury-free conditions (Ph3PAuNTf2 0.5–5 mol %, THF, rt or 60 °С),...

Efficient gold(I)-catalyzed oxidation of COR 2 -functionalized internal alkynes to vicinal tricarbonyl compounds by 2,6-dichloropyridine N-oxide proceeds under mild conditions (DCM, rt). This catalytic reaction provides a good to excellent yielding route to diverse tricarbonyls such as α,β-diketoesters, 1,2,3-triketones, and α,β-diketoamides. The utility of these compounds was also demonstrated by facile one-pot synthesis of important azaheterocyclic systems.

The gold‐catalyzed interplay between cyanamides and ynamides demonstrates condition‐dependent mechanistic dichotomy. [2+2+2] Cycloaddition proceeds under kinetically controlled conditions to give 2,4,6‐triaminopyrimidines (19 examples, up to 99%). Under thermodynamically controlled conditions, the reactivity switches from [2+2+2]‐ to [4+2] cycloaddition; the latter [4+2] reaction accomplishes 1,3‐diaminoisoquinolines (19 examples, up to 97%). The advantages of both methods include regioselectivity, mild reaction conditions (even for the thermodynamically controlled [4+2] reaction) and the possibility of introducing a variety of dialkyl, diaryl, and heterocyclic amino substituents into the target pyrimidine and isoquinoline cores. The reactions were conducted on gram scales and the versatility of the obtained products was demonstrated by post‐functionalizations.magnified image

The gold-catalyzed reaction between benzofuroxans, functioning as nitrene transfer reagents, and N-allylynamides leads to 3-azabicyclo[3.1.0]­hexan-2-imines. This highly selective annulation proceeds smoothly under mild conditions (5 mol % Ph3PAuNTf2, PhCl, 60 °C) and exhibits high functional group tolerance (21 examples, ≤96% yields). The obtained cyclopropanated products represent a useful synthetic platform with an easily modulated substitution pattern as illustrated by their postmodifications. Intramolecular cyclopropanation of gold α-imino carbene intermediates is suggested as a key step of the catalytic cycle.