A Desulfonylative Approach in Oxidative Gold Catalysis: Regiospecific Access to Donor‐Substituted Acyl Gold Carbenes

Abstract

Donor-substituted acyl gold carbenes are challenging to access selectively by gold-promoted intermolecular oxidation of internal alkynes as the opposite regioisomers frequently predominate.B yu sing alkynyl sulfones or sulfonates as substrates,the oxidative gold catalysis in the presence of substituted pyridine N-oxides offers regiospecific access to acyl/aryl, acyl/alkenyl, and acyl/alkoxy gold carbenes by in situ expulsion of sulfur dioxide.T he intermediacies of these reactive species are established by their reactivities,i ncluding undergoing further oxidation by the same oxidant, cyclopropanation of styrenes,e ngaging in a[ 3 + +2] cycloaddition with a-methylstyrene,and conversion into dienones. Scheme 1. A) Oxidative gold catalysis:af acile, non-diazoaccess to a-oxo gold carbenes. B) Examples of regioselective oxidativeg old catalysis with the optimized ratios shown.Scheme 2. Adesulfonylative approach toward exclusive generation of the typically minor a-oxo gold carbene intermediates.

Tandem Transformations via Friedel–Crafts Acylation Followed by a Ring-Expansion, Ring-Opening, and Cycloisomerization Sequence

“…In contrast to the gold-catalyzed cycloisomerization of allenyl ketones to cyclohexyl-fused furans, 9 the microwave-assisted heating conditions smoothly cycloisomerize cyclopentyl-substituted allenyl ketones to cyclohexyl-fused furans 7 via a thermal ring-expansion strategy. 10 The use of cyclohexyl-substituted β-chlorovinyl ketones did not provide the ring-expansion/cycloisomerization products. Instead, the formation of dienyl ketones (E,E)-8 was accomplished in 65−81% yields (Scheme 7).…”

From Amines to Alkynes – Lighting the Way

“…Continuing with the evaluation of the reaction scope, several alkynyl tosylates 6 were prepared from terminal 30 and silyl protected alkynes 43 via the literature procedures. Phenyl derivatives with electron-donating (31,35) as well as mildly electron-withdrawing substituents (32,33,34) reacted equally well (Scheme 3).…”

“…High selectivity of alkyl radicals towards electrophilic alkynyl tosylates compared with terminal alkynes, presented opportunity for the synthesis of unsymmetrical dialkynes via regioselective functionalization (40). Finally, silyl (42) and alkyl (43,44) substituted alkynes were also possible to obtain in workable yields, without additional optimization.…”

Gold‐Catalyzed Intermolecular Oxidative Diyne Cyclizations via 1,6‐Carbene Transfer

“…[2] If appropriate precursors are used, gold carbenes are generated, which enable the design of many useful transformations. [3] Recently, carbene to carbene transformations to obtain vinyl gold carbenes [4] or benzyl gold carbenes [5] were reported. Frist, an alkyne can be activated via π-coordination, then an 1,2-migration/ oxidation generates gold carbenes.…”

“…Without N-oxides we only detected decomposition of the substrate. After that we investigated the effect of different ligands (entries [4][5][6][7][8]. Among a series of different phosphane ligands Me 4 t BuXPhoxAuCl turned out to be the best candidate, leading to 46% yield (entry 8).…”