Indium(III)-catalyzed Aza-Conia-Ene Reaction for the Synthesis of Indolizines

Rhodium(III)-Catalyzed Intramolecular Annulation and Aromatization for the Synthesis of Pyrrolo[1,2-a]quinolines

A rhodium(III)-catalyzed protocol for the synthesis of pyrrolo[1,2-a]quinolines through intramolecular annulation of o-alkynyl amino aromatic ketones and subsequent aromatization is reported. This transformation builds the pyrrole and quinoline moieties of the pyrrolo[1,2-a]quinoline in one pot and achieves a flexible introduction of different substituent groups at 4- and 5-positions on products that were difficult to prepare by other means. The reaction proceeds smoothly on a gram scale, and the products are amenable to downstream synthetic manipulations.

Synthesis of Pyrrolo[2,1-a]isoquinolines through Cu-Catalyzed Condensation/Addition/Oxidation/Cyclization Cascade

We have developed a copper-catalyzed synthesis of pyrrolo[2,1-a]isoquinolines with terminal alkynes, aldehydes, and tetrahydroisoquinolines. A variety of pyrrolo[2,1-a]isoquinolines have been prepared in 17-69% yield via a condensation/Mannich-type addition/oxidation/cyclization cascade sequence. Modifications through simple chemical transformations provided highly functionalized molecules containing a privileged framework.

Diversity-Oriented Metal-Free Synthesis of Nitrogen-Containing Heterocycles Using Atropaldehyde Acetals as a Dual C3/C2-Synthon

A highly efficient and elegant diversity-oriented reaction paradigm employing atropaldehyde acetals as new dual C2/C3 synthons was developed under metal-free conditions using glycine esters as the counterpart reagents, which allowed rapid synthesis of two important nitrogen-containing heterocycles, pyrrolo[1,2-a]quinolines and 3,5-diarylpyridines. The divergent products are subtly controlled by the manipulation of the substitutional groups of glycine esters. When a N-arylglycine ester was used, pyrrolo[1,2-a]quinolines can be formed through cascade oxidative C-C cleavage/multiple cyclization. Instead, N-benzylglycine ester as the counter-reagent led to the synthesis of 3,5-diarylpyridines via two key C-N cleavages. Mild conditions, broad substrate scope, scalability and environmentally acceptable organic solvents rendered this method practical and attractive.

Palladium catalyzed synthesis of indolizines via the carbonylative coupling of bromopyridines, imines and alkynes

We report herein the development of a palladium-catalyzed, multicomponent synthesis of indolizines. The reaction proceeds via the carbonylative formation of a high energy, mesoionic pyridine-based 1,3-dipole, which can undergo spontaneous cycloaddition with alkynes. Overall, this provides a route to prepare indolizines in a modular fashion from combinations of commercially available or easily generated reagents: 2-bromopyridines, imines and alkynes.

A palladium catalyzed, multicomponent synthesis of indolizines is described via the carbon monoxide driven generation of reactive, pyridine-based 1,3-dipoles.

Regio- and Diastereoselective Indium-Catalyzed Conia-Ene Reaction of ortho-Alkynyl Diketopiperazines to Access Fused Diketopiperazinoindolines

An efficient synthesis of diketopiperazinoindolines through an indium-catalyzed intramolecular 5-exo-dig cyclization of ortho-alkynyl diketopiperazines has been reported. The formation of diketopiperazinoindolines proceeds via a regio- and diastereoselective Conia-ene reaction. This synthetic method opens a new door for easy access to functionalized fused diketopiperazinoindolines in high to excellent yields with exclusive Z diastereoselectivity.

In(OTf)3-Catalyzed One-Pot Tandem Mannich and Conia-Ene Cyclization Reaction of N-Propargyl Amido Alcohols with 1,3-Dicarbonyl Compounds: An Approach To Construct Tetrahydro-1H-pyrrolo[2,1-a]isoindolone-1,1-dicarboxylate and Its Application

A one-pot tandem reaction has been developed for the synthesis of substituted tetrahydropyrroloisoindolone via Mannich reaction of N-propargyl amido alcohols with 1,3-dicarbonyl compounds followed by Conia-ene cyclization reaction in moderate to good yields catalyzed by indium(III)triflate [In(OTf)₃]. The reaction is highly regioselective with an exo-cyclic double bond in the pyrrolidine ring. The substituted tetrahydropyrroloisoindolone can be converted to 5H-pyrrolo[2,1-a]isoindol-5-one via decarboxylative aromatization reaction.

Copper-catalyzed formal [1 + 2 + 2]-annulation of alkyne-tethered diazoacetates and pyridines: access to polycyclic indolizines

A copper-catalyzed formal [1 + 2 + 2]-annulation of alkyne-tethered diazo compounds with pyridines, which affords polycyclic fused indolizine derivatives with broad substrate generality, has been reported.