Gold-Catalysed Oxidative Cycloisomerisation of 1,6-Diyne Acetates to 1-Naphthyl Ketones

Abstract

A synthetic method to prepare 1-naphthyl ketones from gold(i)-catalysed oxidative cycloisomerisation of 1,6-diyne acetates is described. The proposed mechanism involves cyclopropenation–cycloreversion of the 1,6-diyne motif initiated by a 1,2-acyloxy migration. This is followed by nucleophilic attack of the ensuing gold carbenoid species by a molecule of water and autoxidation to give the aromatic product.

Recent Advances in the Gold-Catalyzed Reactions of Propargyl Esters

“…We discovered in a later study that a marked switch in the chemoselective outcome could be achieved in reactions of the perceived conformationally constrained organogold species 30 derived from benzene-tethered 1,6-diyne acetates 28 (Scheme ). In this work, the gold(I) phosphine complex Au-3 -catalyzed reactions of the substrate were shown to undergo oxidative hydrolysis to give a variety of 1-naphthyl ketones 29 in 24–67% yield. The reaction mechanism was outlined to proceed with the gold(I)-catalyzed [2,3]-sigmatropic rearrangement of the substrate to give the gold-carbene species 30 .…”

“…24 We discovered in a later study that a marked switch in the chemoselective outcome could be achieved in reactions of the perceived conformationally constrained organogold species 30 derived from benzene-tethered 1,6-diyne acetates 28 (Scheme 5). 25 In this work, the gold(I) phosphine complex Au-3- Building on this observation, we queried whether the presence of an appropriately placed nucleophile would be able to trap the gold-carbene species initially generated from the 1,6-diyne ester system. Such a scenario would require the anticipated cyclopropenation/cycloreversion pathway that culminates in the 1,6-carbene transfer pathway to become inoperative by either electronic or steric bias or a combination of both.…”

“…Homogeneous catalysis is undoubtedly one of the cornerstones of modern chemical synthesis, and its continuous development has been key to efforts focused on the realization of strategies that enable the efficient and concise assembly of compounds of current biological and materials interest. − Within this broad field of research, one of the main drivers of this progress is transition-metal catalysis, which has provided numerous elegant synthetic methods for complex, exotic molecular structures, such as those seamlessly produced by nature, to be built in an operationally simple and selective manner and with high functional group tolerance. Among the breadth of transition-metal catalysts now available, those based on gold­(I) and gold­(III) stand out due to their ability to exhibit potent σ- and π-Lewis acidity without the problems typically associated with such properties. − ,− The group 11 metal also has a high tolerance to air and moisture and various acid-sensitive functional groups that allows for generally mild reaction conditions to be developed. Added to this is the continuous revealing of new reactivities not seen in other d-block elements due to relativistic effects, which reaches a maximum with gold. , Reflective of this has been the impact of gold catalysis on the reaction chemistry of propargyl esters that has made the compound class an invaluable building block in synthetic method development focused on the rapid increase of molecular complexity in an efficient and selective manner. − Key to this has been the ease with which the gold-carbene species or allenyl ester generated in situ from the 1,2- and 1,3-acyloxy migration of the substrate can be readily telescoped into subsequent cascade bond formation reactions and the assembly of various synthetic targets.…”

“…Added to this is the continuous revealing of new reactivities not seen in other d-block elements due to relativistic effects, which reaches a maximum with gold. , Reflective of this has been the impact of gold catalysis on the reaction chemistry of propargyl esters that has made the compound class an invaluable building block in synthetic method development focused on the rapid increase of molecular complexity in an efficient and selective manner. − Key to this has been the ease with which the gold-carbene species or allenyl ester generated in situ from the 1,2- and 1,3-acyloxy migration of the substrate can be readily telescoped into subsequent cascade bond formation reactions and the assembly of various synthetic targets. In the present Account, we showcase our contributions to this field of reaction discovery directed at revealing new modes of reactivity initiated by a [2,3]- or [3,3]-sigmatropic rearrangement. − ,− It provides an overview of novel synthetic routes to accessing a wide variety of cyclic compounds of potential biological and functional materials value in a single operation driven by homogeneous gold catalysis.…”

Heron8 – The 8th Heron Conference on Reactive Intermediates and Unusual Molecules

“…This formation and utilisation of stabilised gold-carbenoid intermediates is of both synthetic and mechanistic interest. [4] Dasan M. Thammattoor and co-workers (Colby College, USA) describe the photolysis of cyclopropaphenanthrenes as a means to generate carbenes by elimination of phenanthrene. Specifically, exo-1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and the corresponding cyclobutan-1-ol derivative produce (1-hydroxycyclopropyl)carbene and (1-hydroxycyclobutyl)carbene, respectively.…”