Generation of Masked TiII Intermediates from TiIV Amides via β-H Abstraction or Alkyne Deprotonation: An Example of Ti-Catalyzed Nitrene-Coupled Transfer Hydrogenation.

Simple Ti amide complexes are shown to act as sources for masked TiII intermediates via several pathways, as demonstrated through the investigation of a unique Ti-catalyzed nitrene-coupled transfer hydrogenation of 3-hexyne. This reaction proceeds through reduction of azobenzene by a masked TiII catalyst, wherein both amines and 3-hexyne can serve as the hydrogen source/reductant for Ti by forming putative titanaziridines via β-H abstraction or putative titanacyclopentynes via protonolysis, respectively.

[1]  Ian A. Tonks,et al.  Ti-catalyzed ring-opening oxidative amination of methylenecyclopropanes with diazenes† , 2020, Chemical science.

[2]  Jason D. Goodpaster,et al.  Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides. , 2019, ACS catalysis.

[3]  A. Odom,et al.  A silica-supported titanium catalyst for heterogeneous hydroamination and multicomponent coupling reactions. , 2019, Dalton transactions.

[4]  Ian A. Tonks,et al.  Modern applications of low-valent early transition metals in synthesis and catalysis , 2018, Nature Reviews Chemistry.

[5]  K. Mashima,et al.  A New Protocol to Generate Catalytically Active Species of Group 4-6 Metals by Organosilicon-Based Salt-Free Reductants. , 2018, Chemistry.

[6]  S. Doye,et al.  Dimethylamine as a Substrate in Hydroaminoalkylation Reactions. , 2017, Angewandte Chemie.

[7]  Ian A. Tonks,et al.  Titanium redox catalysis: insights and applications of an earth-abundant base metal. , 2017, Dalton transactions.

[8]  A. Rheingold,et al.  Synthesis of Highly Oxygenated Carbocycles by Stereoselective Coupling of Alkynes to 1,3- and 1,4-Dicarbonyl Systems , 2017, Journal of the American Chemical Society.

[9]  T. Cundari,et al.  Redox non-innocence permits catalytic nitrene carbonylation by (dadi)TiNAd (Ad = adamantyl) , 2017 .

[10]  Ian A. Tonks,et al.  Generation of TiII Alkyne Trimerization Catalysts in the Absence of Strong Metal Reductants. , 2017, Organometallics.

[11]  Keishi Yamamoto,et al.  Mechanistic understanding of alkyne cyclotrimerization on mononuclear and dinuclear scaffolds: [4 + 2] cycloaddition of the third alkyne onto metallacyclopentadienes and dimetallacyclopentadienes. , 2016, Dalton transactions.

[12]  B. Noll,et al.  C(sp3 )-H Oxidative Addition and Transfer Hydrogenation Chemistry of a Titanium(II) Synthon: Mimicry of Late-Metal Type Reactivity. , 2016, Angewandte Chemie.

[13]  Juventino J. García,et al.  Catalytic transfer hydrogenation of azobenzene by low-valent nickel complexes: a route to 1,2-disubstituted benzimidazoles and 2,4,5-trisubstituted imidazolines. , 2016, Dalton transactions.

[14]  S. Okamoto.  Synthetic Reactions Using Low-Valent Titanium Reagents Derived from Ti(OR)4 or CpTiX3 (X: O-iPr or Cl) in the Presence of Me3SiCl and Mg , 2016 .

[15]  S. Okamoto.  Synthetic Reactions Using Low-valent Titanium Reagents Derived from Ti(OR)4 or CpTiX3 (X = O-i-Pr or Cl) in the Presence of Me3SiCl and Mg. , 2016, Chemical record.

[16]  A. Comas‐Vives,et al.  Surface Organometallic and Coordination Chemistry Toward Single-Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities , 2016 .

[17]  Christophe Copéret,et al.  Surface Organometallic and Coordination Chemistry toward Single-Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities. , 2016, Chemical reviews.

[18]  M. Schmidtmann,et al.  Efficient access to titanaaziridines by C-H activation of N-methylanilines at ambient temperature. , 2015, Angewandte Chemie.

[19]  D. Mindiola,et al.  Dehydrogenation of hydrocarbons with metal-carbon multiple bonds and trapping of a titanium(II) intermediate. , 2014, Dalton transactions.

[20]  Z. Xia,et al.  Development of CVD Ti-containing films , 2013 .

[21]  W. Schuhmann,et al.  Intrinsic Nitrogen‐doped CVD‐grown TiO2 Thin Films from All‐N‐coordinated Ti Precursors for Photoelectrochemical Applications , 2013 .

[22]  P. Eisenberger,et al.  Tantalum-amidate complexes for the hydroaminoalkylation of secondary amines: enhanced substrate scope and enantioselective chiral amine synthesis. , 2009, Angewandte Chemie.

[23]  M. Tarselli,et al.  Aliphatic imines in titanium-mediated reductive cross-coupling: unique reactivity of Ti(O-i-Pr)4/n-BuLi. , 2009, Organic letters.

[24]  S. Doye,et al.  Titanium-Catalyzed Hydroaminoalkylation of Alkenes by C—H Bond Activation at sp3 Centers in the α-Position to a Nitrogen Atom. , 2009 .

[25]  S. Doye,et al.  Titanium-catalyzed hydroaminoalkylation of alkenes by C-H bond activation at sp3 centers in the alpha-position to a nitrogen atom. , 2009, Angewandte Chemie.

[26]  T. Müller,et al.  Hydroamination: direct addition of amines to alkenes and alkynes. , 2008, Chemical reviews.

[27]  T. Beweries,et al.  Five-membered metallacycles of titanium and zirconium--attractive compounds for organometallic chemistry and catalysis. , 2007, Chemical Society reviews.

[28]  F. Ladipo.  SYNTHESIS AND REACTIVITY OF WELL-CHARACTERIZED LOW-VALENT TITANIUM SPECIES , 2006 .

[29]  W. Baumann,et al.  Five-Membered Titana- and Zirconacyclocumulenes: Stable 1-Metallacyclopenta-2,3,4-trienes , 2005 .

[30]  D. Hashizume,et al.  Synthesis and structure of 1-zirconacyclopent-3-yne complexes without substituents adjacent to the triple bond. , 2004, Journal of the American Chemical Society.

[31]  M. Nishiura,et al.  Isolation and Structural Characterization of 1-Zirconacyclopent-3-yne, Five-Membered Cyclic Alkynes , 2002, Science.

[32]  B. Patrick,et al.  Highly Regioselective Alkyne Cyclotrimerization Catalyzed by Titanium Complexes Supported by Proximally Bridged p-tert-Butylcalix[4]arene Ligands , 1999 .

[33]  K. Kadish,et al.  Synthesis, Electrochemistry, and Imido Transfer Reactions of (TTP)Ti(η2-PhNNPh) , 1998 .

[34]  K. Schenk,et al.  Hydrocarbon Activation with Metal Halides: Zirconium Tetrachloride Catalyzing the Jacobsen Reaction and Assisting the Trimerization of Alkynes via the Formation of η6-Arene−Zirconium(IV) Complexes , 1997 .

[35]  I. P. Rothwell,et al.  Synthesis, Structure, and Reactivity of Aryloxo(imido)titanium Complexes† , 1990 .

[36]  S. F. Pedersen,et al.  The first practical niobium(III) reagent in organic synthesis. A convenient route to 2-amino alcohols via the coupling of imines with aldehydes or ketones promoted by NbCl3(DME) , 1987 .

[37]  T. Nestrick,et al.  Catalytic Transfer Hydrogenation , 1974 .

[38]  Ian A. Tonks,et al.  Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via Ti(II)/Ti(IV) redox catalysis. , 2016, Nature chemistry.

[39]  K. Kadish,et al.  Synthesis, Electrochemistry, and Imido Transfer Reactions of (TTP)Ti(eta(2)-PhN=NPh). , 1998, Inorganic chemistry.

[40]  P. Fanwick,et al.  Formation and characterization of .eta.2-imine and .eta.2-azobenzene derivatives of titanium containing ancillary aryloxide ligation , 1990 .

[41]  C. Floriani,et al.  Titanium tetrachloride binding and making arenes from acetylenes: the synthesis and X-ray crystal structure of a titanium(IV)–hexamethylbenzene complex , 1989 .