Gold-Catalyzed Nitrene Transfer from Benzofuroxans to N-Allylynamides: Synthesis of 3-Azabicyclo[3.1.0]hexanes

Abstract

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.

Modular approach to non-aromatic and aromatic pyrroles through gold-catalyzed [3 + 2] cycloaddition of 2H-azirines and ynamides

“…The generation of carbene intermediates in gold-catalyzed O - and N -transfer reactions is a controversial issue. 69 We did not detect any cyclopropanation 56 products, when the ynamide substrate 2ag , featuring an alkene fragment, was employed (Scheme 8A), or when styrene was added in the reaction mixture containing 1a and 2b (Scheme 8B). In addition, any products derived from CH-insertions 70 or 1,2-shifts 71 were not detected in the gold-catalyzed reaction occurring between hexyl-substituted ynamide 2t and azirine 1a (Table 2).…”

“…In turn, ynamides are customizable, highly reactive alkynes, i.e. C-C diatomic synthons, and some impressive examples of their synthetic applications have been reported in the chemical literature [44][45][46][47][48][49][50][51][52][53][54] (including our recent works in this direction [55][56][57][58][59] ). If the retrosynthetic approach is applied, it would be expected that the integration of 2H-azirines and ynamides could lead to pyrrole products formed via the formal [3 + 2] cycloaddition.…”

Atom-economic synthesis of β-ketosulfones based on gold-catalyzed highly regioselective hydration of alkynylsulfones

“…Based on our previous experience in the gold-catalyzed transformations of alkynes (for recent works see ref. [30][31][32][33][34], we hypothesized that gold-catalyzed hydration of alkynylsulfones can open up a facile general route to β-ketosulfones (Scheme 1C). All our results relevant to this novel 100% atomeconomic synthetic method are detailed in the following sections.…”

Insights into gold-catalyzed formation of aza-heterocycles using benzofuroxans as nitrene transfer reagents: mechanism and origins of chemoselectivity

“…Recently, benzofurazan N-oxides 12 have been considered as an effective and convenient nitrene transfer reagent for the generation of 2-amino-7-nitroindoles from ynamides due to its high reactivity, security, cheapness and accessibility. 13,14 However, compared with other nucleophilic nitrenes, N-oxides used as the precursors of a-imino gold-carbene intermediates for the cyclopropanation are less explored, especially in gold chemistry.…”

“…Scheme 2 Gold-catalyzed annulation of benzofuroxan A1 with N-allylynamide A2 reported by Dubovtsev's group 14. …”