Ruthenium-Catalyzed Tandem Carbene/Alkyne Metathesis/N–H Insertion: Synthesis of Benzofused Six-Membered Azaheterocycles

Abstract

The Cp*RuCl-based catalyst enables expedient access to a variety of benzofused six-membered azaheterocycles from unprotected oalkynylanilines and trimethylsilyldiazomethane through an unprecedent tandem carbene/alkyne metathesis/N−H insertion reaction. The transformation takes place under mild reaction conditions (room temperature, <15 min) and with excellent functional group tolerance. The synthetic utility of the final products and a mechanistic rationale are also discussed.

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

“…The evolution of chemicals through the transition-metal catalyzed reaction is an exciting era for the chemistry of palladium [4], ruthenium [5], platinum [6], etc., and has been significantly adopted by the industry. For example, ruthenium-catalyzed N-H insertion reaction for the formation of benzofused six/five-membered azaheterocycles [7] which have a wide range of significant biological activity, such as anti-bacterial, -fungal, -tubercular, helminthic, -plasmodial, -cancer, -inflammatory, cardiotonic, -hypertensive, -thrombotic, histaminic, -ulcer, analgesic, neuroleptic, etc. [8].…”

Isocyanate-free Polyurea Synthesis via Ru-Catalyzed Car-bene Insertion into the N‒H Bonds of Urea

“…[13][14][15] Using amines as precursor, a recent article by Ihara and coworkers has reported on the synthesis of polyamines through ruthenium catalyzed N-H insertion, a continuation of the research on the synthetic utility of C-N bond formation using diazo compounds. [16][17][18][19][20][21] Ureas have been used as nucleophiles in transition metal catalysis such as Pd-catalyzed carboaminations and more recently as nitrene precursors in Ru-catalyzed C-H amination. [22][23][24][25] Therefore, we envisioned the possibility of using N-H insertions to synthesize polyureas as shown below (Scheme 1e).…”

Tunable Synthesis of Indeno[1,2-c]furans and 3-Benzoylindenones via FeCl3-Catalyzed Carbene/Alkyne Metathesis Reaction of o-Alkynylbenzoyl Diazoacetates

“…Among them, transition-metal-catalyzed carbene/alkyne metathesis (CAM) turns out to be a straightforward tool for the construction of complex polycyclic skeletons in one pot . In this regard, CAM reactions using diazo compounds as the carbene precursors have attracted widespread attention due to its easy accessibility and high reactivity. − However, it was also noticed that most of these methods have to be accomplished in the presence of noble metal catalysts such as gold, rhodium, ruthenium, and copper, and the toxicity and scarcity of these catalysts could be the main restrictive factors for the sustainability of these methods, especially in large-scale applications. Therefore, finding low-cost yet still effective catalysts to promote the CAM reactions is urgently needed.…”

“…First, iron carbene I is formed through iron-catalyzed dinitrogen expulsion of o -alkynylbenzoyl diazoacetate 1a . This is followed by 5 -exo-dig carbocyclization to afford vinyl iron carbene II . − Next, II is terminated with a formal [3 + 2] cycloaddition to give product 2a . , On the other hand, II is terminated with O–H insertion to form the intermediate III , , which undergoes an oxidant dehydrogenation to afford product 3a (Scheme , path a). As an alternative pathway, 2a might undergo a furan ring opening under the assistance of water to afford intermediate IV .…”