Vicinal diboronates in high enantiomeric purity through tandem site-selective NHC-Cu-catalyzed boron-copper additions to terminal alkynes.

A Cu-catalyzed protocol for conversion of terminal alkynes to enantiomerically enriched diboronates is reported. In a single vessel, a site-selective hydroboration of an alkyne leads to the corresponding terminal vinylboronate, which undergoes a second site-selective and enantioselective hydroboration. Reactions proceed in the presence of 2 equiv of commercially available bis(pinacolato)diboron [B(2)(pin)(2)] and 5-7.5 mol % loading of a chiral bidentate imidazolinium salt, affording diboronates in 60-93% yield and up to 97.5:2.5 enantiomeric ratio (er). The enantiomerically enriched products can be functionalized to afford an assortment of versatile organic molecules. Enynes are converted to unsaturated diboronates with high chemo- (>98% reaction of alkyne; <2% at alkene) and enantioselectivity (e.g., 94.5:5.5 er).

[1]  P. Andersson,et al.  Iridium-catalyzed enantioselective hydrogenation of vinyl boronates. , 2009, Chemical communications.

[2]  J. Morken,et al.  Pt-catalyzed enantioselective diboration of terminal alkenes with B2(pin)2. , 2009, Journal of the American Chemical Society.

[3]  J. Yun,et al.  Highly regio- and enantioselective copper-catalyzed hydroboration of styrenes. , 2009, Angewandte Chemie.

[4]  A. Hoveyda,et al.  Stereogenic-at-metal Zn- and Al-based N-heterocyclic carbene (NHC) complexes as bifunctional catalysts in Cu-free enantioselective allylic alkylations. , 2009, Journal of the American Chemical Society.

[5]  Li Dang,et al.  Boryl ligands and their roles in metal-catalysed borylation reactions. , 2009, Chemical communications.

[6]  A. Hoveyda,et al.  Efficient boron-copper additions to aryl-substituted alkenes promoted by NHC-based catalysts. enantioselective Cu-catalyzed hydroboration reactions. , 2009, Journal of the American Chemical Society.

[7]  A. Hoveyda,et al.  Enantioselective total synthesis of clavirolide C. Applications of Cu-catalyzed asymmetric conjugate additions and Ru-catalyzed ring-closing metathesis. , 2008, Journal of the American Chemical Society.

[8]  Li Dang,et al.  DFT Studies on the Borylation of α,β-Unsaturated Carbonyl Compounds Catalyzed by Phosphine Copper(I) Boryl Complexes and Observations on the Interconversions between O- and C-Bound Enolates of Cu, B, and Si , 2008 .

[9]  H. Doucet.  Suzuki–Miyaura Cross-Coupling Reactions of Alkylboronic Acid Derivatives or Alkyltrifluoroborates with Aryl, Alkenyl or Alkyl Halides and Triflates , 2008 .

[10]  Dennis G. Gillingham,et al.  Highly site- and enantioselective Cu-catalyzed allylic alkylation reactions with easily accessible vinylaluminum reagents. , 2008, Journal of the American Chemical Society.

[11]  J. Morken,et al.  Catalytic enantioselective diboration, disilation and silaboration: new opportunities for asymmetric synthesis. , 2007, Chemical communications.

[12]  I. Beletskaya,et al.  Element-element additions to unsaturated carbon-carbon bonds catalyzed by transition metal complexes. , 2006, Chemical reviews.

[13]  J. Morken,et al.  Rh-catalyzed enantioselective diboration of simple alkenes: reaction development and substrate scope. , 2005, The Journal of organic chemistry.

[14]  P. Guiry,et al.  The Development of Enantioselective Rhodium‐Catalysed Hydroboration of Olefins , 2005 .

[15]  J. Morken,et al.  Catalytic enantioselective hydrogenation of vinyl bis(boronates). , 2004, Journal of the American Chemical Society.

[16]  Steven P. Miller,et al.  Rhodium-catalyzed enantioselective diboration of simple alkenes. , 2003, Journal of the American Chemical Society.

[17]  T. Shimada,et al.  Asymmetric synthesis of 1-aryl-1,2-ethanediols from arylacetylenes by palladium-catalyzed asymmetric hydrosilylation as a key step. , 2002, Journal of the American Chemical Society.

[18]  N. Miyaura,et al.  A borylcopper species generated from bis(pinacolato)diboron and its additions to α,β-unsaturated carbonyl compounds and terminal alkynes , 2001 .

[19]  W. Weissensteiner,et al.  Rhodium catalysed enantioselective hydroboration of alkenylboronic esters with catecholborane , 1996 .