Transition-Metal-Catalyzed Organic Reactions Using Bromoalkynes

Transition-metal-catalyzed organic reactions for the formation ofcarbon–heteroatom and carbon–carbon bonds form the basis of essential and powerfulstrategies for the preparation of important compounds in pharmaceutical, biological,and materials sciences. Bromoalkynes, easily prepared from terminal alkynes withNBS in almost quantitative yields, is one kind of the most important intermediates andversatile building blocks in organic synthesis. We envisagedtransition-metal-catalyzed organic reactions by using1-bromoalkynes. The followingcontents were included.(1) CuI-Catalyzed Suzuki Coupling Reaction of Organoboronic Acids withAlkynyl Bromides：In the presence of CuI (10mol%) and8-hydroxyquinoline (20mol%), organoboron derivatives including aromatic and alkenyl boronic acids,potassium aryltrifluoroborates and sodium tetraphenylborate reacted smoothly with1-bromo-2-substituted acetylene to generate the corresponding cross-couplingproducts in good to excellent yields in C2H5OH. It is important to note that aromaticN,O-ligand8-hydroxyquinoline is the most effective ligand for the reaction(2) CuI-Catalyzed Cross-Coupling Reaction of Terminal Alkynes with1-Bromoalkynes: A facile synthesis of unsymmetrical1,3-butadiynes from terminalalkynes and1-bromoalkynes in the presence of CuI and P(o-Tol)3was developed andgood yields of the corresponding cross-coupling products were obtained under mildand simple reaction conditions. The scope and limitation of the cross–couplingreaction were also investigated.(3) The Sequential and One-Pot Reactions of Phenols with Bromoalkynes for theSynthesis of (Z)-2-Bromovinyl Phenyl Ethers and Benzo[b]furans：Benzo[b]furanswere prepared in one pot based on the addition/palladium-catalyzed C–H bondfunctionalization of phenols with bromoalkynes. The addition reactions of phenols tobromoalkynes generated (Z)-2-bromovinyl phenyl ethers in high yields with excellent region-and stereoselectivity. The obtained (Z)-2-bromovinyl phenyl etherssubsequently proeded by intramolecular cyclization to afford2-substitutedbenzo[b]furans in good yields through palladium-catalyzed direct C–H bondfunctionalizations. It is important to note that the transformation of phenols withbromoalkynes into benzo[b]furans could be carried out in one pot with a simple andefficient tandem procedure.