Bifu Liu

Synthesis of Amides via Palladium-Catalyzed Amidation of Aryl Halides

A new and efficient method for the synthesis of amides via palladium-catalyzed C-C coupling of aryl halides with isocyanides is reported, by which a series of amides were formed from readily available starting materials under mild conditions. This transformation could extend its use to the synthesis of natural products and significant pharmaceuticals.

Palladium-Catalyzed Intermolecular Aerobic Oxidative Cyclization of 2-Ethynylanilines with Isocyanides: Regioselective Synthesis of 4-Halo-2-aminoquinolines

A robust and regioselective palladium-catalyzed intermolecular aerobic oxidative cyclization of 2-ethynylanilines with isocyanides to the synthesis of 4-halo-2-aminoquinolines is reported herein. The procedure constructs various 4-halo-2-aminoquinolines with moderate to excellent yields (47-94%) and broad substrates scope. Furthermore, this process can be easily extended to synthesis of various 6H-indolo[2,3-b]quinolines via an intramolecular Buchwald-Hartwig cross-coupling reaction in two-step one-pot manner.

Palladium‐Catalyzed Bromoalkynylation of CC Double Bonds: Ring‐Structure‐Dependent Synthesis of 7‐Alkynyl Norbornanes and Cyclobutenyl Halides

The development of efficient and sustainable procedures for the synthesis of complex molecules is an important task in modern organic chemistry. The direct cleavage of an alkynyl– halogen bond followed by the reconnection of both the alkynyl and halogen ions with the two carbon atoms of an unsaturated carbon–carbon bond provides ready access to highly functionalized products from simple alkynes with excellent atom economy. We previously achieved highly regioand stereoselective bromoalkynylation of internal alkynes for the synthesis of conjugated cis-bromoalkenynes. Subsequent research on this subject revealed a further use of bromoalkynes in complex molecule synthesis. Norbornene derivatives are an appealing group of organic molecules that are convenient starting materials for the synthesis of polymers, solar-energy-storage materials, and bioactive products. In addition, their strained structure and high potential to coordinate to transition metals, as well as their possible industrial applications have attracted considerable research interest. Thus, we decided to react phenylethynyl bromide (2a) with norbornene (1a), expecting to obtain 2-bromo-3-(2-phenylethynyl)bicyclo[2.2.1]heptane (3aa ; Scheme 1). However, when using the previously optimized conditions, we did not detect the formation of 3aa, instead we obtained 2-bromo-7-(2-phenylethynyl)bicyclo[2.2.1]heptane (3a) in excellent yield, as confirmed by H NMR spectroscopy. This unexpected result attracted our interest, since, to the best of our knowledge, no example of a direct 7-alkynyl bromonorbornane formation has been reported. From previous reports, we realized that after the formation of the nonclassical “norbornonium” cation, the C-7 functionalization can be achieved through a nucleophile rearrangement (Scheme 2). Our success in synthesizing C-7-

Palladium-catalyzed tandem reaction of o-aminophenols, bromoalkynes and isocyanides to give 4-amine-benzo[b][1,4]oxazepines

A robust route to 4-amine-benzo[b][1,4]oxazepines relying upon a palladium-catalyzed tandem reaction of o-aminophenols, bromoalkynes and isocyanides has been developed. This chemistry presumably proceeds through the migratory insertion of isocyanides into the vinyl-palladium intermediate as a key step.

Synthesis of 2-Aminobenzoxazoles and 3-Aminobenzoxazines via Palladium-Catalyzed Aerobic Oxidation of o-Aminophenols with Isocyanides

A Pd-catalyzed aerobic oxidation of o-aminophenols and isocyanides for the synthesis of 2-aminobenzoxazoles and 3-aminobenzoxazines has been achieved in an air atmosphere. The procedure constructs 2-aminobenzoxazoles and 3-aminobenzoxazines with moderate to excellent yields and a broad substrate scope. Apart from experimental simplicity, this methodology has the advantages of mild reaction conditions and easily accessible starting materials. Furthermore, the utility of this method has also been successfully applied to the synthesis of other types of useful nitrogen heterocycles.

An efficient synthesis of 2,5-diimino-furans via Pd-catalyzed cyclization of bromoacrylamides and isocyanides.

A novel palladium-catalyzed cyclization of bromoacrylamides with isocyanides gives substituted 2,5-diimino-furans, which can be used as the precursor of maleamides. This synthesis likely proceeds, after isonitrile insertion into C–Pd(II) bond, through the coordination of the amide oxygen atom to the Pd(II) centre as a key step.

Synthesis of 6-aminophenanthridines via palladium-catalyzed insertion of isocyanides into N-sulfonyl-2-aminobiaryls

A robust route to a diverse set of 6-aminophenanthridines via palladium-catalyzed C–H activation of N-sulfonyl-2-aminobiaryl and isocyanide insertion is reported. This transformation could also provide an important approach for building core frameworks of conjugated organic polymer materials.

Synthesis of Polysubstituted 3-Amino Pyrroles via Palladium-Catalyzed Multicomponent Reaction

A novel approach for the synthesis of polysubstituted 3-amino pyrroles via palladium-catalyzed three-component tandem reaction was developed. The procedure constructs various polysubstituted 3-amino pyrroles with moderate to excellent yields under mild reaction conditions with assembly efficiency, readily available starting materials, and good functional group tolerance. Furthermore, this process was successfully applied to the synthesis of different 3-phenyl-1,4-dihydropyrrolo[3,2-b]indole derivatives via an intramolecular Buchwald-Hartwig cross-coupling reaction in two steps.