@inbook {SCHAFER2020405, title = {Titanium catalyzed synthesis of amines and N-heterocycles}, booktitle = {Advances in Organometallic Chemistry}, volume = {74}, year = {2020}, pages = {405-468}, publisher = {Academic Press}, organization = {Academic Press}, abstract = {

Titanium is an earth abundant inexpensive early transition metal that has been used extensively in industrial polyolefin synthesis, but rarely applied toward the synthesis of fine chemicals. Recent advances have shown the usefulness of titanium catalyzed reactions in the catalytic synthesis of amines and N-heterocycles by both hydroamination and hydroaminoalkylation. These atom economic transformations can be coupled with other reactive bond insertion processes to realize catalytic multicomponent coupling reactions to generate more complex products. Alternatively, sequential catalytic protocols can be accomplished in one-pot to achieve efficient transformations, further emphasizing titanium catalysis as an under-utilized metal for Green Chemistry. Titanium also has multiple oxidation states that are accessible and have been featured in stoichiometric reactions over the past 40 years. More recently new strategies for taking advantage of oxidative addition/reductive elimination protocols and radical chemistry has resulted in new catalytic approaches. Throughout the highlighted work titanium offers complementary reactivity to established late transition metal protocols. However, ligand modified reactivity remains poorly understood and the development of predictive tools for understanding how ligands influence electronic properties at the metal center will advance efforts to realize new catalytic reactions. Furthermore, strategic ligand designs that control the steric environment about the titanium metal center to promote stereoselective transformations are desirable. Due to the extensive exploration of fundamental stoichiometric transformations with titanium complexes over the years, there are many attractive reactions that await creative insights for the realization of catalytic variants.

}, keywords = {Green chemistry, HYDROAMINATION, HYDROAMINOALKYLATION, Hydrofunctionalization, Multicomponent coupling, One-pot reactions, Redox-relay reactions, Reductive coupling}, issn = {0065-3055}, doi = {https://doi.org/10.1016/bs.adomc.2020.04.003}, url = {https://www.sciencedirect.com/science/article/pii/S0065305520300162}, author = {Laurel L. Schafer and Manfred Man{\ss}en and Peter M. Edwards and Erica K.J. Lui and Samuel E. Griffin and Christine R. Dunbar}, editor = {Pedro J. P{\'e}rez} } @article {31533, title = {Ti-Catalyzed Hydroamination for the Synthesis of Amine-Containing π-Conjugated Materials}, journal = {Chemistry {\textendash} A European Journal}, volume = {24}, year = {2018}, pages = {5562-5568}, abstract = {

Abstract A series of conjugated enamines were prepared by Ti catalyzed anti-Markovnikov hydroamination. The synthetic route is efficient with yields of up to 94\ \% and the 100\ \% atom efficiency of the reaction means that these products are easily isolated and purified. Due to the extended conjugated system, the enamine tautomers were observed exclusively in both solid and solution phases, as determined by X-ray crystallography and NMR spectroscopy. These new conjugated molecules, with N incorporated into the backbone, show interesting photophysical properties including photo-luminescent quantum yields of up to 0.26. Notably, through the incorporation of B to give a donor\–acceptor π-conjugated system, a redshift of approximately 100 nm is observed for the emission maximum along with the anticipated solvatochromic shifts.

}, keywords = {conjugated oligomers, enamine, HYDROAMINATION, TITANIUM, π-conjugated materials}, doi = {10.1002/chem.201704500}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201704500}, author = {Hao, Han and Thompson, Kyle A. and Hudson, Zachary M. and Schafer, Laurel L.} } @article {ADSC:ADSC201500861, title = {Facile Synthesis and Isolation of Secondary Amines via a Sequential Titanium(IV)-Catalyzed Hydroamination and Palladium-Catalyzed Hydrogenation}, journal = {Advanced Synthesis \& Catalysis}, volume = {358}, number = {5}, year = {2016}, pages = {713{\textendash}718}, publisher = {WILEY-VCH Verlag}, keywords = {HYDROAMINATION, HYDROGENATION, palladium on carbon, sequential reactions, TITANIUM CATALYSTS}, issn = {1615-4169}, doi = {10.1002/adsc.201500861}, url = {http://dx.doi.org/10.1002/adsc.201500861}, author = {Lui, Erica K. J. and Schafer, Laurel L.} } @article {EJIC:EJIC201501272, title = {Hydroelementation of Unsaturated C{\textendash}C Bonds Catalyzed by Metal Scorpionate Complexes}, journal = {European Journal of Inorganic Chemistry}, volume = {2016}, number = {15-16}, year = {2016}, pages = {2391{\textendash}2402}, abstract = {Tridentate scorpionate ligands have a rich history in coordination chemistry. In the past two decades, metal complexes bearing scorpionate ligands have found increasing utility as catalysts for a variety of useful transformations. This microreview focuses on the utility of scorpionate ligands in hydroelementation of carbon{\textendash}carbon unsaturated bonds, focusing specifically on hydrothiolation, hydroamination, hydroalkoxylation and hydrophosphinylation of alkenes and alkynes. In each example, the solid phase and solution phase coordination and fluxionality of the scorpionate ligand will be discussed.}, keywords = {ALKENES, ALKYNES, Hydroalkoxylation, HYDROAMINATION, Hydroelementation, Hydrophosphinylation, Hydrothiolation, Scorpionate ligands}, issn = {1099-0682}, doi = {10.1002/ejic.201501272}, url = {http://dx.doi.org/10.1002/ejic.201501272}, author = {Wathier, Matthew and Love, Jennifer A.} } @article {2622, title = {Bis- and Mono(amidate) Complexes of Yttrium: Synthesis, Characterization, and Use as Precatalysts for the Hydroamination of Aminoalkenes}, journal = {Organometallics}, volume = {28}, number = {14}, year = {2009}, note = {ISI Document Delivery No.: 473AWTimes Cited: 11Cited Reference Count: 47Stanlake, Louisa J. E. Schafer, Laurel L.}, month = {Jul}, pages = {3990-3998}, type = {Article}, abstract = {A high-yielding synthetic route is disclosed for yttrium bis- and mono(amidate) complexes using the reaction of amide proligand and Y(N(SiMe3)(2))(3) starting materials. The structure, bonding, and solution phase characterization data for this new class of complexes are presented. The modular nature of the amidate ligand allows for easy addition of electron-withdrawing CF3 groups in the ligand backbone to tune electronic properties of the resulting precatalysts. The amidate ligands in the bis(amidate) complexes were found to be highly fluxional on the NMR time scale, while the mono(amidate) yttrium complex required heating to 110 degrees C before ligand redistribution was observed. Three bis(amidate) complexes with differing electronic properties and one mono(amidate) complex have been used as precatalysts for hydroamination using a wide range of aminoalkene substrates. Bis(amidate) complexes bearing the more electron-withdrawing amidate ligands were found to be the most active precatalysts for intramolecular alkene hydroamination.}, keywords = {ALKENES, AMIDATE COMPLEXES, ASYMMETRIC HYDROAMINATION, EARTH, GROUP-3, HYDROAMINATION, INTRAMOLECULAR, LANTHANIDE, LIGANDS, metals, OLEFINS, ORGANOLANTHANIDE-CATALYZED HYDROAMINATION}, isbn = {0276-7333}, url = {://000268176700006}, author = {Stanlake, L. J. E. and Schafer, L. L.} } @article {2491, title = {The Direct Synthesis of Unsymmetrical Vicinal Diamines from Terminal Alkynes: A Tandem Sequential Approach for the Synthesis of Imidazolidinones}, journal = {Synthesis-Stuttgart}, number = {1}, year = {2009}, note = {ISI Document Delivery No.: 395LSTimes Cited: 6Cited Reference Count: 84Lee, Alison V. Sajitz, Melanie Schafer, Laurel L.Sp. Iss. SI}, month = {Jan}, pages = {97-104}, type = {Article}, abstract = {The combination of titanium-catalyzed anti-Markovnikov hydroamination of terminal alkynes with the Strecker reaction is used in the synthesis of unsymmetrical vicinal diamines via the one-pot synthesis of alpha-cyanoamines. This methodology is Further applied to the efficient synthesis of imidazolidinones. An easy-to-use bis(amidate)titanium precatalyst permits efficient approaches to heterocyclic chemistry from terminal alkynes.}, keywords = {AMINES, ANTI-MARKOVNIKOV, ASYMMETRIC-SYNTHESIS, CATALYZED INTERMOLECULAR HYDROAMINATION, HETEROCYCLES, HYDROAMINATION, IMIDO COMPLEXES, INTRAMOLECULAR HYDROAMINATION, LIGANDS, SCOPE, tandem reactions, TITANIUM, TITANIUM PRECATALYST, VINYLARENES}, isbn = {0039-7881}, url = {://000262526200012}, author = {Lee, A. V. and Sajitz, M. and Schafer, L. L.} } @article {2494, title = {N,O-Chelates of Group 4 Metals: Contrasting the Use of Amidates and Ureates in the Synthesis of Metal Dichlorides}, journal = {European Journal of Inorganic Chemistry}, number = {18}, year = {2009}, note = {ISI Document Delivery No.: 467LNTimes Cited: 5Cited Reference Count: 69Leitch, David C. Beard, J. David Thomson, Robert K. Wright, Vincent A. Patrick, Brian O. Schafer, Laurel L.}, month = {Jun}, pages = {2691-2701}, type = {Article}, abstract = {A series of dichloride complexes of titanium and zirconium with amidate and ureate ancillary ligands have been prepared, Three examples of bis(amidate)dichlorotitanium and zirconium complexes were effectively synthesized through salt metathesis with metal tetrachloride as starting materials. Optimum results were achieved using sodium amidate salts formed from sodium bis(trimethylsilyl)amide and neutral amide proligands, while other methods were ineffective. Use of electron-donating ureate ligands in lieu of amidates enables preparation through alternate routes. Protonolysis of Ti(NMe2)(2)Cl-2 and Zr(NMe2)(2)Cl-2(dme) with urea proligands leads to dichlorobis(ureate) complexes in good yield. Using a tethered bis(ureate) ligand eliminates the fluxional behaviour and coordination isomerism observed for both bis(amidate) and bis(ureate) zirconium complexes. ((C) Wiley-VCH Verlag GmbH \& Co. KGaA, 69451 Weinheim, Germany, 2009)}, keywords = {amidate, BIS(AMIDATE) TITANIUM PRECATALYST, CATALYTIC, Chelates, COORDINATION CHEMISTRY, EARLY, GUANIDINATE LIGANDS, HYDROAMINATION, INTERMOLECULAR HYDROAMINATION, N, O ligands, OLEFIN POLYMERIZATION, SOLUTION DYNAMICS, STRUCTURAL-CHARACTERIZATION, TITANIUM, TRANSITION-METALS, Ureate, ZIEGLER-NATTA POLYMERIZATION, ZIRCONIUM}, isbn = {1434-1948}, url = {://000267740500015}, author = {Leitch, D. C. and Beard, J. D. and Thomson, R. K. and Wright, V. A. and Patrick, B. O. and Schafer, L. L.} } @article {2408, title = {Tantalum-Amidate Complexes for the Hydroaminoalkylation of Secondary Amines: Enhanced Substrate Scope and Enantioselective Chiral Amine Synthesis}, journal = {Angewandte Chemie-International Edition}, volume = {48}, number = {44}, year = {2009}, note = {ISI Document Delivery No.: 513DPTimes Cited: 9Cited Reference Count: 25Eisenberger, Patrick Ayinla, Rashidat O. Lauzon, Jean Michel P. Schafer, Latcrel L.}, pages = {8361-8365}, type = {Article}, keywords = {ALKENES, ALKYLATION, alpha, amidates, BOND, C-H ACTIVATION, CATALYSIS, CATALYTIC HYDROAMINOALKYLATION, enantioselectivity, homogeneous, HYDROAMINATION, HYDROAMINOALKYLATION, IMINE, LIGANDS, tantalum, UNACTIVATED OLEFINS}, isbn = {1433-7851}, url = {://000271302900038}, author = {Eisenberger, P. and Ayinla, R. O. and Lauzon, J. M. P. and Schafer, L. L.} } @article {1332, title = {Bis(amidate) titanium precatalyst for the intermolecular hydroamination of allenes}, journal = {Inorganica Chimica Acta}, volume = {359}, number = {9}, year = {2006}, note = {ISI Document Delivery No.: 052YITimes Cited: 25Cited Reference Count: 64}, month = {Jun}, pages = {3097-3102}, type = {Article}, abstract = {A bis(amidate)-bis(amido) titanium complex (5) is an efficient precatalyst for the regioselective intermolecular hydroamination of substituted allenes. Arylamines react quickly with a 5 mol\% precatalyst loading at 90 degrees C to give the ketimine product, which can be reduced to give substituted amines. With precatalyst loading of 10 mol\% and temperatures of 120 degrees C alkyl amines can be used as viable substrates for the hydroamination of substituted allenes. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {ALKENES, allenes, amidate ligands, AMIDO COMPLEXES, CATALYST, CYCLIZATION, HYDROAMINATION, IMIDO COMPLEXES, INTRAMOLECULAR HYDROAMINATION, NITROGEN-HETEROCYCLES, ORGANOLANTHANIDE-CATALYZED HYDROAMINATION, precatalyst, TERMINAL ALKYNES, titanium complex, UNPROTECTED AMINO OLEFINS, VINYLARENES}, isbn = {0020-1693}, url = {://000238269600063}, author = {Ayinla, R. O. and Schafer, L. L.} } @article {1456, title = {Group 4 bis(pyrimidinoxide) complexes. Investigations of electronic effects in catalytic hydroamination}, journal = {Organometallics}, volume = {25}, number = {22}, year = {2006}, note = {ISI Document Delivery No.: 094IJTimes Cited: 22Cited Reference Count: 130Lee, Alison V. Schafer, Laurel L.}, month = {Oct}, pages = {5249-5254}, type = {Review}, abstract = {Substituted pyrimidinols, acidic aromatic alcohols, were used as proligands to synthesize metal complexes of Ti and Zr. These new pseudotetrahedral complexes were investigated as catalysts for the hydroamination of alkynes and alkenes. The stabilized anion of the pyrimidinoxide ligand results in enhanced electrophilicity at the metal center. These electronically modified complexes are catalytically active, but their enhanced reactivity results in reduced selectivity in comparison with the related bis(phenoxide) complexes in alkyne hydroamination. This reactivity was used to advantage in the cyclohydroamination of select aminoalkene substrates with the Zr bis(pyrimidinoxide) complex.}, keywords = {ALKENES, ANTI-MARKOVNIKOV HYDROAMINATION, ARYLOXIDE, BIS(AMIDATE) TITANIUM PRECATALYST, HYDROAMINATION, IMIDO COMPLEXES, INTERMOLECULAR, LIGANDS, MEDIATED INTRAMOLECULAR, OXIDATIVE AMINATION, TERMINAL ALKYNES}, isbn = {0276-7333}, url = {://000241232800013}, author = {Lee, A. V. and Schafer, L. L.} } @article {1601, title = {A pentagonal pyramidal zirconium imido complex for catalytic hydroamination of unactivated alkenes}, journal = {Organometallics}, volume = {25}, number = {17}, year = {2006}, note = {ISI Document Delivery No.: 070PZTimes Cited: 66Cited Reference Count: 40Thomson, Robert K. Bexrud, Jason A. Schafer, Laurel L.}, month = {Aug}, pages = {4069-4071}, type = {Article}, abstract = {The first, isolable group 4 imido complexes capable of promoting intramolecular olefin hydroamination for the preparation of N-containing heterocycles are presented. The structurally characterized 6-coordinate bis(amidate)-supported zirconium imido complex is a rare example of distorted-pentagonal-pyramidal geometry.}, keywords = {ALKYNE HYDROAMINATION, allenes, AMIDATE COMPLEXES, BIS(AMIDATE) TITANIUM PRECATALYST, C-H ACTIVATION, HYDROAMINATION, INTERMOLECULAR HYDROAMINATION, INTRAMOLECULAR, REACTIVITY, TEMPERATURE, TI(NME2)(4)}, isbn = {0276-7333}, url = {://000239536800007}, author = {Thomson, R. K. and Bexrud, J. A. and Schafer, L. L.} } @article {1060, title = {Intramolecular hydroamination of unactived olefins with Ti(NMe2)(4) as a precatalyst}, journal = {Organic Letters}, volume = {7}, number = {10}, year = {2005}, note = {ISI Document Delivery No.: 924NCTimes Cited: 104Cited Reference Count: 59}, month = {May}, pages = {1959-1962}, type = {Article}, abstract = {[GRAPHICS] Commercially available Ti(NMe2)(4) has been used effectively as a precatalyst in a facile protocol for the intramolecular hydroamination of aminoalkenes to yield pyrrolidine and piperidine heterocyclic products with isolated yields up to 92\%. Germinally substituted substrates display the highest reactivity. This precatalyst is also effective for the hydroamination of activated internal alkenes, providing access to more complex heterocyclic target molecules.}, keywords = {ALKENE HYDROAMINATION, ALKYNE, AMIDO COMPLEXES, ANTI-MARKOVNIKOV, CATALYZED INTERMOLECULAR HYDROAMINATION, GROUP-3 METALS, HYDROAMINATION, IMIDO COMPLEXES, REACTIVITY, TITANIUM, ZIRCONIUM}, isbn = {1523-7060}, url = {://000228984500019}, author = {Bexrud, J. A. and Beard, J. D. and Leitch, D. C. and Schafer, L. L.} } @article {1287, title = {Structure, bonding, and reactivity of Ti and Zr amidate complexes: DFT and X-ray crystallographic studies}, journal = {Inorganic Chemistry}, volume = {44}, number = {24}, year = {2005}, note = {ISI Document Delivery No.: 986ZLTimes Cited: 21Cited Reference Count: 75}, month = {Nov}, pages = {8680-8689}, type = {Article}, abstract = {Easily prepared and highly modular organic amide proligands have been used to synthesize a series of new bis(amidate)-bis(amido) Ti and Zr complexes via protonolysis. These complexes have been structurally characterized by NMR spectroscopy and X-ray crystallography. The solid-state molecular structures of these complexes indicate that the amidate ligands bind to the metal centers in an exclusively bidentate fashion, resulting in discrete monomeric species. Geometric isomerism in these species is highly dependent upon the steric characteristics of the proligands utilized in the synthesis. In solution, these complexes are observed to isomerize on the NMR time scale, with one isomer being predominant. Bonding in the bis(amidate)-bis(amido) complexes was investigated by DFT calculations. The geometric isomers predicted by theory matched the experimentally observed results, within experimental error. The orbitals associated with amidate-metal bonding are energetically well below the frontier orbitals. The HOMO in these complexes is a pi orbital associated with amido ligand-to-metal bonding character, while the LUMO in all cases is a vacant d orbital on the metal center.}, keywords = {ALKYNYL GROUPS, C-H BONDS, ENHANCED REACTIVITY, HYDROAMINATION, IMIDO COMPLEXES, INTERMOLECULAR, OLEFIN POLYMERIZATION, PROPYLENE POLYMERIZATION, SI-H, TITANIUM CATALYSTS, ZIRCONIUM(IV) COMPLEXES}, isbn = {0020-1669}, url = {://000233488100008}, author = {Thomson, R. K. and Zahariev, F. E. and Zhang, Z. and Patrick, B. O. and Wang, Y. A. and Schafer, L. L.} } @article {1287, title = {Structure, bonding, and reactivity of Ti and Zr amidate complexes: DFT and X-ray crystallographic studies}, journal = {Inorg. Chem.}, volume = {44}, number = {24}, year = {2005}, note = {ISI Document Delivery No.: 986ZLTimes Cited: 21Cited Reference Count: 75}, month = {Nov}, pages = {8680-8689}, type = {Article}, abstract = {

Easily prepared and highly modular organic amide proligands have been used to synthesize a series of new bis(amidate)-bis(amido) Ti and Zr complexes via protonolysis. These complexes have been structurally characterized by NMR spectroscopy and X-ray crystallography. The solid-state molecular structures of these complexes indicate that the amidate ligands bind to the metal centers in an exclusively bidentate fashion, resulting in discrete monomeric species. Geometric isomerism in these species is highly dependent upon the steric characteristics of the proligands utilized in the synthesis. In solution, these complexes are observed to isomerize on the NMR time scale, with one isomer being predominant. Bonding in the bis(amidate)-bis(amido) complexes was investigated by DFT calculations. The geometric isomers predicted by theory matched the experimentally observed results, within experimental error. The orbitals associated with amidate-metal bonding are energetically well below the frontier orbitals. The HOMO in these complexes is a pi orbital associated with amido ligand-to-metal bonding character, while the LUMO in all cases is a vacant d orbital on the metal center.

}, keywords = {ALKYNYL GROUPS, C-H BONDS, ENHANCED REACTIVITY, HYDROAMINATION, IMIDO COMPLEXES, INTERMOLECULAR, OLEFIN POLYMERIZATION, PROPYLENE POLYMERIZATION, SI-H, TITANIUM CATALYSTS, ZIRCONIUM(IV) COMPLEXES}, isbn = {0020-1669}, url = {://000233488100008}, author = {Thomson, R. K. and Zahariev, F. E. and Zhang, Z. and Patrick, B. O. and Y. A. Wang* and L. L. Schafer*} } @article {1286, title = {Synthesis, characterization, and reactivity of the first hafnium alkyl complex stabilized by amidate ligands}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {83}, number = {6-7}, year = {2005}, note = {ISI Document Delivery No.: 963UVTimes Cited: 7Cited Reference Count: 20}, month = {Jun}, pages = {1037-1042}, type = {Article}, abstract = {A photo and thermally stable bis(amidate)-dibenzyl complex of Hf ([(DMP)(NO)(Ph)](2)Hf(CH2Ph)(2)(THF) (2a) was formed as a monosolvated THF adduct in near quantitative yield from Hf(CH2Ph)(4) and N-2,6-dimethylphenyl(phenyl)amide (1). Isomerization between the THF-bound product and the THF-free product can be observed visually by the conversion from a red-orange product at low temperatures to a pale yellow product at high temperatures. Solid-state crystallographic characterization of the orange product confirmed its constitution as a monosolvated species. Kinetic parameters for the exchange of the THF moiety were determined from variable-temperature NMR experiments. The product of the hydrolysis of the Hf dibenzyl species by water was characterized by X-ray crystallography, and was found to be a rare tetrametallic Hf oxo cluster species (3).}, keywords = {amidate, CHEMISTRY, COORDINATION CHEMISTRY, CRYSTAL, exchange processes, hafnium, HYDROAMINATION, MOLECULAR-STRUCTURE, organometallic, protonolysis, TITANIUM}, isbn = {0008-4042}, url = {://000231832500064}, author = {Thomson, R. K. and Patrick, B. O. and Schafer, L. L.} } @article {947, title = {Carbon-nitrogen bond formation via the reaction of terminal alkynes with a dinuclear side-on dinitrogen complex}, journal = {Journal of the American Chemical Society}, volume = {126}, number = {31}, year = {2004}, note = {ISI Document Delivery No.: 843TSTimes Cited: 27Cited Reference Count: 21}, month = {Aug}, pages = {9480-9481}, type = {Article}, keywords = {ACTIVATION, COORDINATION, FIXATION, FUNCTIONALIZATION, HETEROCYCLES, HYDROAMINATION, METAL-COMPLEXES, MOLECULAR NITROGEN, MOLYBDENUM, N-2}, isbn = {0002-7863}, url = {://000223110100007}, author = {Morello, L. and Love, J. B. and Patrick, B. O. and Fryzuk,Michael D.} }