Photoinduced Radical Annulations of Tetrahydroisoquinoline Derivatives with 2-Benzothiazolimines: Highly Diastereoselective Synthesis of Fused Hexahydroimidazo[2,1-a]isoquinolines.

We report herein a photoinduced radical 1,3-dipolar cycloaddition between the 2-benzothiazolimines and tetrahydroisoquinoline derivatives with an organo-photocatalyst. A variety of benzothiazole-based hexahydroimidazo[2,1-a]isoquinoline architectures with great synthetic value were conveniently and efficiently constructed in moderate to good yields and excellent diastereoselectivities with highly tolerant functional groups. Moreover, the practicality and utility of this protocol were demonstrated by scale-up synthesis and facile elaboration. Preliminary mechanistic investigations indicated that the reaction proceeded via a visible-light-induced radical 1,3-dipolar cycloaddition pathway. This finding is expected to stimulate a more extensive exploration of the green and concise synthesis of structurally diverse heterocyclic molecules in the synthetic community.

Gold-Catalyzed Intramolecular Hydroarylation and Transfer Hydrogenation of N-Aryl Propargylamines to Construct Tetrahydroquinolines and 5,6-Dihydro-4H-pyrrolo[3,2,1-ij]quinolines.

A novel protocol of gold-catalyzed N-aryl propargylamines to construct tetrahydroquinolines and 5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolines in moderate to good yields has been developed through the tandem reactions of intramolecular hydroarylation and transfer hydrogenation. The strategy has the advantages of easy access to raw materials, simple reaction conditions, good substrate compatibility, high efficiency, and excellent regioselectivity.

Ruthenium-Catalyzed Enantioselective Hydrogenation of 9-Phenanthrols.

The enantioselective hydrogenation of arenols to corresponding chiral cyclic alcohols remains a challenge because of their aromaticity and the difficulty in controlling the regio-, chemo-, and stereoselectivity. In this work, the first highly efficient ruthenium-catalyzed enantioselective hydrogenation of 9-phenanthrols has been successfully realized under mild conditions via trapping the unstable keto tautomers. The method provides a facile access to a range of chiral 9,10-dihydrophenanthren-9-ols with up to 98 % yield and >99 % ee. The hydrogenation pathway includes base-promoted tautomerization of 9-phenanthrols and Ru-catalyzed asymmetric hydrogenation of the in situ generated unstable keto tautomers.

Oxidative cyanation of N-aryltetrahydroisoquinoline induced by visible light for the synthesis of α-aminonitrile using potassium thiocyanate as a "CN" agent.

A novel method for the synthesis of α-aminonitrile through visible-light-induced oxidative cyanation of N-aryltetrahydroisoquinoline with potassium thiocyanate has been developed. The process does not require the use of a photocatalyst, transition metal reagent, strong oxidizing agent, or toxic cyano-containing compound, which makes the reaction simple and green.

Copper-catalyzed oxidative cross-coupling of α-aminocarbonyl compounds with primary amines toward 2-oxo-acetamidines.

A general and mild method for the construction of a carbon-nitrogen bond via copper-catalyzed oxidative cross-coupling of amines with α-aminocarbonyl compounds was achieved. Amines, either aliphatic primary amines, aromatic primary amines or secondary amines can be used as the starting materials. When R2 was different from R3, two isomers would be observed. Therefore, this reaction system has a broad substrate scope and provides a facile pathway for the synthesis of 2-oxo-acetamidines.

PhI(OAc)2-mediated 1,2-aminohalogenation of alkynes: a general access to (E)-4-(halomethylene)oxazolidin-2-ones.

A new PhI(OAc)2-mediated 1,2-aminohalogenation of prop-2-yn-1-yl carbamates and various halogen sources is presented with excellent selectivity and high step-economy. The reaction is general and rapid for the construction of diverse (E)-4-(halomethylene)oxazolidin-2-ones through the generation of the three-membered ring or N-radical followed by intramolecular cyclization.

Hypervalent iodine-triggered transformation of homopropargyl sulfonamides into dihalo-2,3-dihydropyrroles.

A novel hypervalent iodine-triggered hydroamination of homopropargyl sulfonamides with copper halides to obtain dihalo-2,3-dihydropyrroles was efficiently developed. The reaction can provide access to chloro/bromo-cyclization extended from iodocyclization to prepare potentially useful halogenated building blocks for drug development with broad functional group tolerance and high yield yet in a short time.

Fast regioselective sulfonylation of pyridine/quinoline N-oxides induced by iodine.

Fast sulfonylation of pyridine/quinoline N-oxides induced by iodine is demonstrated herein. The regioselective protocol occurs under metal-free conditions in a short reaction time (10 min), exhibiting high efficiency (up to 92% yield) and good compatibility (up to 33 examples). A gram-scale reaction was conducted with only a slight loss of production.

Copper/Silver Cocatalyzed Oxidative Coupling of Vinylarenes with ICH2CF3 or ICH2CHF2 Leading to ß-CF3/CHF2-Substituted Ketones.

A novel copper/silver cocatalyzed oxidative coupling of vinylarenes with ICH2CF3 or ICH2CHF2 through a radical process has been developed. The transformation provides an attractive approach to ß-CF3/CHF2-substituted ketones, with the advantages of easily available starting materials and operational simplicity.

Copper/Iron-Catalyzed Aerobic Oxyphosphorylation of Terminal Alkynes Leading to ß-Ketophosphonates.

A copper/iron-catalyzed oxyphosphorylation of alkynes with H-phosphonates through a radical process was developed. The present protocol provides an attractive approach to ß-ketophosphonates in moderate to good yields, with the advantages of readily available substrate, high functional group tolerance and operation simplicity.

Method for transforming alkynes into (E)-dibromoalkenes.

The highly stereoselective bromination of alkynes has been realized by using copper(II) bromide as both the reacting partner and the catalyst, offering a generally efficient synthesis of (E)-dibromoalkenes. The reaction conditions are exceptionally mild, and a wide range of functional groups are well tolerated.