N-Pyridinyl Sulfilimines as a Source for α-Imino Gold Carbenes: Access to 2-Amino-Substituted N-Fused Imidazoles

Abstract

Gold-catalyzed formal 1,3-dipolar annulation between readily accessible N-pyridinylsulfilimines and ynamides is reported. A diverse set of imidazole derivatives is prepared from the corresponding sulfilimines and ynamides. These functionalized cyclic products can undergo further transformations to afford diverse imidazole frameworks. Moreover, in situ synthesis is feasible and shows good potential in the synthesis of nucleoside analogues.

α‐Imino Gold Carbene Intermediates from Readily Accessible Sulfilimines: Intermolecular Access to Structural Diversity

“…Conjugated ylides that can offer 1,3‐dipoles are prone to undergo [3+2] annulations with C≡C bonds (Scheme B, path a). In this context, the reaction between ynamides and sulfilimines with pyridinyl groups on the nitrogen atoms can deliver imidazopyridines by trapping the α‐imino gold carbenes with another nitrogen atom . Gold(III) catalysts are more efficient than gold(I) catalysts in this transformation.…”

Gold‐Catalyzed Stereoselective Domino Cyclization/Alkynylation of N‐Propargylcarboxamides with Benziodoxole Reagents for the Synthesis of Alkynyloxazolines

“…were less efficient, affording 3 b in lower yields (entry [13][14][15]. Changing the additive to Zn(OTf) 2 , Yb (OTf) 3 , Sc(OTf) 2 , NaOAc, or Na 2 CO 3 , and 2-picolinic acid significantly decreased the yield (entry [16][17][18][19][20][21]. Another EBX derivative (4 a) did also afford 3 b, but in Under the optimized conditions (1.2 equiv.…”

“…[16] Inspired by this, we envisaged a domino process (Scheme 1b) on the basis of our previous studies on the gold-catalyzed cyclization of propargylamides (Scheme 2) [5g] and onepot strategies based on this reactivity. [17]…”

Acyl Migration versus Epoxidation in Gold Catalysis: Facile, Switchable, and Atom‐Economic Synthesis of Acylindoles and Quinoline Derivatives

“…Either an attack at the nitrogen atom forms a-imino gold carbenes and subsequent C À H insertions gives 7-acylindoles (Scheme 1, entry 2), [9b] or this versatile reagent undergoes oxygen attack to give quinoline oxides through seven-membered ring intermediates (Scheme 1, entry 3). [9i] Inspired by previous reports, [9][10][11] we herein report the unprecedented site-selective trapping of such a-imino gold carbenes for a divergent synthesis of acylindoles or epoxides via selective acyl shifts and epoxidations (Scheme 1, entry 4).…”

“…The development of efficient synthetic methods through a-imino gold carbene intermediates has become an important tool for the construction of heterocycles. Gold-promoted nitrene transfer from nucleophilic nitrene equivalents, such as pyridine-based aza-ylides, [6] azides, [7] 2H-azirines, [8] isoxazole derivatives, [9] and sulfilimines [10] to alkynes, generates a-imino gold carbenes. These can efficiently undergo nucleophilic attack, CÀH insertion, or cyclopropanation.…”