Regioselectivity in the reaction of tantalum-unsymmetrical acetylene complexes with carbonyl compounds. Stereoselective preparation of 1-alkenyl sulfides, .alpha.,.beta.-unsaturated esters, and amides
摘要:
Tantalum-alkyne complexes, derived by treatment of alkynes with low-valent tantalum (TaCl5 and zinc), react in situ with carbonyl compounds to give (E)-allylic alcohols stereoselectively. When unsymmetrical acetylenes are employed in the reaction, two regioisomeric allylic alcohols are produced. The regioselectivity of the reaction depends on the steric and electronic effects of the substituents on the acetylenes. For example, treatment of tantalum-alkyne complexes derived from methyl alkynyl sulfides with carbonyl compounds yields (E)-3-hydroxy-1-propenyl methyl sulfides in a regioselective manner. Tantalum-alkyne complexes derived from acetylenic esters react with carbonyl compounds regioselectively at the alpha-position of the esters to give Z-isomers of trisubstituted alpha,beta-unsaturated esters. In contrast, tantalum-alkyne complexes derived from acetylenic amides react with carbonyl compounds predominantly at the beta-position of the amides. The regioselectivity of the reaction between acetylenic amides and aldehydes, however, cannot be explained solely in terms of the steric and electronic effects of the substituents. Strong coordination of the amide group to the tantalum center could also be responsible for the observed selectivity, which is opposite to that observed with tantalum-acetylenic ester complexes.
Process for preparing alkynyl-substituted aromatic and heterocyclic compounds
申请人:Miller A. Joseph
公开号:US20050137402A1
公开(公告)日:2005-06-23
Mono- and disubstituted aryl or heterocyclic acetylenes are produced by a process comprising reacting an aryl nitrile with an alkynylzinc compound, a bis-alkynylzinc compound, or an alkynylmagnesium compound, in the presence of a nickel/phosphine catalyst.
Alkynylation of benzonitriles via nickel catalyzed C–C bond activation
作者:Jonathan M. Penney、Joseph A. Miller
DOI:10.1016/j.tetlet.2004.02.163
日期:2004.6
The scope of synthetically useful nickel catalyzed cross coupling reactions of benzonitriles has now been expanded to allow alkynylation. Thus, the cross coupling of benzonitriles with alkynylzinc reagents occurs readily in the presence of Ni/PMe3 based catalysts to afford the respective aryl alkynes in high yields. (C) 2004 Elsevier Ltd. All rights reserved.
US7105707B2
申请人:——
公开号:US7105707B2
公开(公告)日:2006-09-12
Sulfonated N-Heterocyclic Carbenes for Pd-Catalyzed Sonogashira and Suzuki-Miyaura Coupling in Aqueous Solvents
作者:Sutapa Roy、Herbert Plenio
DOI:10.1002/adsc.200900886
日期:——
of the respective disulfonated N‐heterocyclic carbene (NHC) precursors in reasonable yields (46–77%). Water‐soluble palladium catalyst complexes, in situ obtained from the respective sulfonated imidazolinium salt, sodium tetrachloropalladate (Na2PdCl4) and potassium hydroxide (KOH) in water, were successfully applied in the copper‐free Sonogashiracoupling reaction in isopropyl alcohol/water mixtures
Regioselectivity in the reaction of tantalum-unsymmetrical acetylene complexes with carbonyl compounds. Stereoselective preparation of 1-alkenyl sulfides, .alpha.,.beta.-unsaturated esters, and amides
Tantalum-alkyne complexes, derived by treatment of alkynes with low-valent tantalum (TaCl5 and zinc), react in situ with carbonyl compounds to give (E)-allylic alcohols stereoselectively. When unsymmetrical acetylenes are employed in the reaction, two regioisomeric allylic alcohols are produced. The regioselectivity of the reaction depends on the steric and electronic effects of the substituents on the acetylenes. For example, treatment of tantalum-alkyne complexes derived from methyl alkynyl sulfides with carbonyl compounds yields (E)-3-hydroxy-1-propenyl methyl sulfides in a regioselective manner. Tantalum-alkyne complexes derived from acetylenic esters react with carbonyl compounds regioselectively at the alpha-position of the esters to give Z-isomers of trisubstituted alpha,beta-unsaturated esters. In contrast, tantalum-alkyne complexes derived from acetylenic amides react with carbonyl compounds predominantly at the beta-position of the amides. The regioselectivity of the reaction between acetylenic amides and aldehydes, however, cannot be explained solely in terms of the steric and electronic effects of the substituents. Strong coordination of the amide group to the tantalum center could also be responsible for the observed selectivity, which is opposite to that observed with tantalum-acetylenic ester complexes.