Controlling the selectivity and efficiency of the hydrogen borrowing reaction by switching between rhodium and iridium catalysts.

The catalytic alkylation of ketones with alcohols via the hydrogen borrowing methodology (HB) has the potential to be a highly efficient approach for forming new carbon-carbon bonds. However, this transformation can result in more than one product being formed. The work reported here utilises bidentate triazole-carbene ligated iridium and rhodium complexes as catalysts for the selective formation of alkylated ketone or alcohol products. Switching from an iridium centre to a rhodium centre in the complex resulted in significant changes in product selectivity. Other factors - base, base loading, solvent and reaction temperature - were also investigated to tune the selectivity further. The optimised conditions were used to demonstrate the scope of the reaction across 17 ketones and 14 alcohols containing a variety of functional groups. A series of mechanistic investigations were performed to probe the reasons behind the product selectivity, including kinetic and deuterium studies.

[1]  R. Kempe,et al.  3d-Metal Catalyzed N- and C-Alkylation Reactions via Borrowing Hydrogen or Hydrogen Autotransfer. , 2018, Chemical reviews.

[2]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[3]  D. Milstein,et al.  Manganese-Catalyzed α-Alkylation of Ketones, Esters, and Amides Using Alcohols , 2018, ACS catalysis.

[4]  A. Goeppert,et al.  Regioselective deuteration of alcohols in D2O catalysed by homogeneous manganese and iron pincer complexes , 2018 .

[5]  D. Roy,et al.  Recent Advances in Palladium‐Catalyzed Cross‐Coupling Reactions at ppm to ppb Molar Catalyst Loadings , 2018 .

[6]  B. Çetinkaya,et al.  Iridium(I)-Catalyzed Alkylation Reactions To Form α-Alkylated Ketones. , 2018, The Journal of organic chemistry.

[7]  D. Banerjee,et al.  Nickel-Catalyzed Phosphine Free Direct N-Alkylation of Amides with Alcohols. , 2018, The Journal of organic chemistry.

[8]  D. Young,et al.  Switchable Chemoselective Transfer Hydrogenations of Unsaturated Carbonyls Using Copper(I) N-Donor Thiolate Clusters. , 2018, The Journal of organic chemistry.

[9]  A. Corma,et al.  Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis. , 2018, Chemical reviews.

[10]  W. Brennessel,et al.  Catalytic Upgrading of Ethanol to n-Butanol via Manganese-Mediated Guerbet Reaction , 2018 .

[11]  M. D. Mbaye,et al.  Alkylation of Ketones Catalyzed by Bifunctional Iron Complexes: From Mechanistic Understanding to Application , 2017 .

[12]  B. Messerle,et al.  Highly Efficient Rh(I) Homo- and Heterogeneous Catalysts for C-N Couplings via Hydrogen Borrowing. , 2017, Inorganic chemistry.

[13]  Rui Wang,et al.  RhCl(CO)(PPh3)2 catalyzed α-alkylation of ketones with alcohols , 2017 .

[14]  K. Venkatasubbaiah,et al.  Isolation and Characterization of Regioisomers of Pyrazole-Based Palladacycles and Their Use in α-Alkylation of Ketones Using Alcohols , 2017 .

[15]  J. Gooding,et al.  Iridium(III) homo- and heterogeneous catalysed hydrogen borrowing C–N bond formation , 2017 .

[16]  P. Boyle,et al.  Catalytic Acceptorless Dehydrogenation of Amines with Ru(PR2NR′2) and Ru(dppp) Complexes , 2017 .

[17]  Guoqi Zhang,et al.  Cobalt-Catalyzed α-Alkylation of Ketones with Primary Alcohols. , 2017, Organic letters.

[18]  G. Chelucci.  Ruthenium and osmium complexes in CC bond-forming reactions by borrowing hydrogen catalysis , 2017 .

[19]  Miguel Peña‐López,et al.  Manganese-Catalyzed Hydrogen-Autotransfer C-C Bond Formation: α-Alkylation of Ketones with Primary Alcohols. , 2016, Angewandte Chemie.

[20]  R. Kempe,et al.  General and Mild Cobalt-Catalyzed C-Alkylation of Unactivated Amides and Esters with Alcohols. , 2016, Journal of the American Chemical Society.

[21]  F. Glorius,et al.  Ruthenium-NHC Catalyzed α-Alkylation of Methylene Ketones Provides Branched Products through Borrowing Hydrogen Strategy , 2016 .

[22]  Pavel A. Dub,et al.  The mechanism of enantioselective ketone reduction with Noyori and Noyori-Ikariya bifunctional catalysts. , 2016, Dalton transactions.

[23]  Q. Wang,et al.  Rhodium-catalyzed alkylation of ketones and alcohols with alcohols , 2016, Russian Journal of General Chemistry.

[24]  Fei Huang,et al.  C-Alkylation of Ketones and Related Compounds by Alcohols: Transition-Metal-Catalyzed Dehydrogenation. , 2016, Angewandte Chemie.

[25]  M. V. Jiménez,et al.  Oxidation and β-Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N-Heterocyclic Carbene Ligands. , 2015, Chemistry.

[26]  Feng Li,et al.  Synthesis of a-Alkylated Ketones via Tandem Acceptorless Dehydrogenation/a-Alkylation from Secondary and Primary Alcohols Catalyzed by Metal-Ligand Bifunctional Iridium Complex [Cp*Ir(2,2'-bpyO)(H2O)]. , 2015, The Journal of organic chemistry.

[27]  C. Gunanathan,et al.  Ruthenium Catalyzed Selective α- and α,β-Deuteration of Alcohols Using D2O. , 2015, Organic letters.

[28]  John Leonard,et al.  A Survey of the Borrowing Hydrogen Approach to the Synthesis of some Pharmaceutically Relevant Intermediates , 2015 .

[29]  Feng Li,et al.  α-Alkylation of ketones with primary alcohols catalyzed by a Cp*Ir complex bearing a functional bipyridonate ligand. , 2014, The Journal of organic chemistry.

[30]  Y. Obora.  Recent Advances in α-Alkylation Reactions using Alcohols with Hydrogen Borrowing Methodologies , 2014 .

[31]  Xicheng Wang,et al.  Direct α-alkylation of ketones with alcohols in water. , 2014, ChemSusChem.

[32]  Jianping Liu,et al.  Catalyst-free dehydrative α-alkylation of ketones with alcohols: green and selective autocatalyzed synthesis of alcohols and ketones. , 2014, Angewandte Chemie.

[33]  T. Constantieux,et al.  An iron/amine-catalyzed cascade process for the enantioselective functionalization of allylic alcohols. , 2013, Angewandte Chemie.

[34]  M. Kantam,et al.  Tris(acetylacetonato)rhodium(III)‐Catalyzed α‐Alkylation of Ketones, β‐Alkylation of Secondary Alcohols and Alkylation of Amines with Primary Alcohols , 2013 .

[35]  S. Pan,et al.  Recent Advances in Iridium-Catalyzed Alkylation of C–H and N–H Bonds , 2013 .

[36]  Fan Wu,et al.  Ketone formation via mild nickel-catalyzed reductive coupling of alkyl halides with aryl acid chlorides. , 2012, Organic letters.

[37]  D. Weix,et al.  Synthesis of functionalized dialkyl ketones from carboxylic acid derivatives and alkyl halides. , 2012, Organic letters.

[38]  A. Lei,et al.  Bond formations between two nucleophiles: transition metal catalyzed oxidative cross-coupling reactions. , 2011, Chemical reviews.

[39]  Laura J. Allen,et al.  Green alcohol couplings without transition metal catalysts: base-mediated β-alkylation of alcohols in aerobic conditions , 2010 .

[40]  R. Crabtree,et al.  Dehydrogenation as a substrate-activating strategy in homogeneous transition-metal catalysis. , 2010, Chemical reviews.

[41]  Yoichi M. A. Yamada,et al.  Development of a convoluted polymeric nanopalladium catalyst: α-alkylation of ketones and ring-opening alkylation of cyclic 1,3-diketones with primary alcohols , 2007 .

[42]  M. Yus,et al.  Easy α-alkylation of ketones with alcohols through a hydrogen autotransfer process catalyzed by RuCl2(DMSO)4 , 2006 .

[43]  Yoichi M. A. Yamada,et al.  A solid-phase self-organized catalyst of nanopalladium with main-chain viologen polymers: alpha-alkylation of ketones with primary alcohols. , 2006, Organic letters.

[44]  P. Andersson,et al.  Mechanistic aspects of transition metal-catalyzed hydrogen transfer reactions. , 2006, Chemical Society reviews.

[45]  M. Yus,et al.  [Ru(DMSO)4]Cl2 catalyzes the α-alkylation of ketones by alcohols , 2005 .

[46]  J. Otera,et al.  Modern Carbonyl Chemistry , 2000 .

[47]  Joop A. Peters,et al.  Meerwein-Ponndorf-Verley Reductions and Oppenauer Oxidations: An Integrated Approach , 1994 .