Yibiao Li

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.

Copper(I)-Catalyzed Synthesis of 2,5-Disubstituted Furans and Thiophenes from Haloalkynes or 1,3-Diynes

A regioselective synthesis of 2,5-disubstituted furans using copper(I) catalyst from haloalkynes in a one-pot procedure has been reported. This chemistry proceeds through the hydration reaction of 1,3-diynes, which can be readily prepared from the coupling reaction of haloalkynes in the presence of CuI. The procedure also can be used for the facile synthesis of 2,5-disubstituted thiophenes.

Palladium‐Catalyzed Sequential Formation of CC Bonds: Efficient Assembly of 2‐Substituted and 2,3‐Disubstituted Quinolines

A series of substituted quinolines was prepared from arylamines, aldehydes, and terminal olefins (see scheme). The palladium-catalyzed sequential formation of C-C bonds proceeds smoothly with both electron-deficient and electron-rich olefins. When acrylic acid is used as terminal olefin, decarboxylation occurs to provide 2-substituted quinolines.

Expedient Synthesis of Functionalized Conjugated Enynes: Palladium-Catalyzed Bromoalkynylation of Alkynes†

The construction of C(sp) C(sp) bonds is an important method for the synthesis of various conjugated structures and biologically active compounds. Among different protocols for achieving this goal, the coupling between substituted alkenes and terminal alkynes stands as the most widely used method. However, the synthesis of functionalized alkenynes is problematic because of the potential of the desired functional group to react with the catalytic system. In this context, a more expedient and favored, although still underdeveloped, route to form this structure is the direct addition of an “activated” alkyne to other alkynes. To this end, several groups have reported novel catalytic systems for alkynylcyanation, alkynylstannylation, and alkynylboranation reactions, which simplified the original strategies (Scheme 1a). Therefore, the importance of the search for more direct alkynylation modes is evident.

Silver-Catalyzed Difunctionalization of Terminal Alkynes: Highly Regio- and Stereoselective Synthesis of (Z)-β-Haloenol Acetates

A new silver-catalyzed highly regio- and stereoselective difunctionalization reaction of simple terminal alkynes was reported in which the (Z)-beta-haloenol acetate derivatives were formed efficiently. The resulting products were versatile intermediates in organic synthesis.

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.

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.