Competing Intra‐ vs Intermolecular Nitrene Transfer in the [Au]‐Catalysed Reaction of 2‐Alkynylphenylazides

Abstract

The possibility of interrupting the gold‐catalysed intramolecular cyclization of 2‐alkynylphenylazide derivatives, employing known nitrene transfer reagents such as anthranil and its isomer 1,2‐benzisoxazole, has been attempted in search of developing simple tools for product diversification. With 1,2‐benzisoxazoles, the intermolecular nitrene transfer leading to quinazoline is competitive with intramolecular azidoalkyne cyclization resulting in spiro indol‐3‐ylidene derivatives. However, in case of the reaction in the presence of anthranil, both intra‐ and intermolecular nitrene transfer processes result in the same product indol‐3‐ylidene.

Synthesis, characterization, and crystal structure of 2-(2-azidophenyl)-3-oxo-3H-indole 1-oxide

“…As part of our efforts to demonstrate the reactivity of the nitro group compared to the azide group (Dhote & Ramana, 2022;Dhote, Halner et al, 2021), we designed a substrate that incorporates both a nitro group and an azide group positioned ortho to an alkyne functionality. Interestingly, when we subjected this substrate to treatment with either Au III or Au I , we obtained isatogen 2 with the azide moiety intact in relatively good yield (see reaction scheme below).…”

Advances in gold catalyzed synthesis of quinoid heteroaryls

“…Additionally, their investigation into solvent selection revealed that neither nonpolar nor highly polar solvents yielded satisfactory results. 68 …”

Construction of the quinobenzoxazine coreviagold-catalyzed dual annulation of azide-tethered alkynones with anthranils

“…3,4 In this regard, we have been working on understanding the competitive formation of α-imino vs. α-oxo gold carbene intermediates, as well as inter vs. intramolecular nitrene transfers. 5 For example, we have recently documented how the established intramolecular nitrene transfer in o -azido alkynes could be prevailed over by an intermolecular nitrene transfer. 5 c In continuation of our efforts in this direction, we looked at a similar possibility with the azidoalkyne cyclization of 1-(2-azidophenyl)prop-2-yn-1-ones ( o -azidoacetylenic ketones) in the presence of anthranil as an external nitrogen transfer agent.…”

“…of 1-(2-azidophenyl)-3-phenylprop-2-yn-1-one 1a and 1.2 equiv. of anthranil 2a in the presence of 5 mol% AuCl 3 in 1,2-dichloroethane (1,2-DCE) at rt (entry 1, Table 1), 5 where the formation of two new products was observed. The minor product that was obtained was found to be the triazole 4a resulting from the undesired intramolecular [3 + 2]-cycloaddition reaction.…”