Sequential One-Pot Carbene-Catalyzed Intramolecular Stetter Reaction and Acid-Mediated Condensation: Access to Heteroatom Analogues of π-Extended Polyaromatic Hydrocarbons

Abstract

In this Letter, we disclose a simple and effective method to access a variety of phenanthro[9,10-b]furan and 1Hdibenzo[e,g]indole derivatives based on the design of a carbenecatalyzed intramolecular Stetter reaction followed by a Paal−Knorr reaction in one-pot. These compounds are a class of π-extended polycyclic aromatic hydrocarbon (PAH) derivatives containing an oxygen/nitrogen atom. The practical utility of the developed transformation was demonstrated on the gram scales and postsynthetic transformations thereof.

Carbene-Catalyzed Tandem Imine Umpolung–Intramolecular Aza-Conjugate Addition–Oxidation to Access N-Substituted Isoindolinones

“…Based on control experiments and literature precedence, − , a plausible mechanism for an NHC-catalyzed tandem imine umpolung–intramolecular aza-Michael addition–oxidation for the synthesis of isoindolinone derivatives is depicted in Scheme . Initially, carbene I is generated by the action of the base on the NHC precatalyst.…”

“…The Douthwaite and co-workers and Rovis and co-workers reported the isolation of the nitrogen analogue of a Breslow intermediate, known as an aza-Breslow intermediate, from a stoichiometric reaction of NHC and imines . Our group and Biju and co-workers, for the first time, developed NHC-catalyzed imine umpolung as a key step to access indoles. , Recently, the NHC-catalyzed umpolung of imines enabling various organic transformations was reported by our group and the research groups of Biju, Fu, Lupton, and Chi . Imines are important building blocks for the synthesis of amides and nitrogen heterocycles .…”

Photocatalyzed Energy Transfer for Atom Economical Synthesis of O‐Bridged Tricyclo‐Fused Cyclopropane Derivatives

“…As part of our ongoing efforts in the synthesis of fused heterocycles/carbocycles using enones, [22] we designed a substrate 1 a, having activated and unactivated alkene moieties tethered to benzene ring; and planned to explore its reactivity in the presence of visible light photoredox catalysis. Initially, 1 a was irradiated with blue LEDs in the presence of photocatalyst Ru(bpy) 3 Cl 2 .6H 2 O.…”

Transition metal-free and temperature dependent one-pot access to phenanthrene-fused heterocycles via a 1,3-dipolar cycloaddition pathway

“…There is a reasonable number of reports on the individual synthesis of phenanthrenes [16][17][18][19][20][21] and pyrazoles. [22][23][24][25][26] For instance, the research group of Wang demonstrated the efficient formation of phenanthrols starting from diphenyl dicarbonyls and tosyl hydrazide under basic conditions (Scheme 1a).…”