Structural Studies of the Low-Valent Titanium “Solution”:  What Goes on in the Pinacol Coupling Reaction?  [J. Am. Chem. Soc. 2001, 123, 1503−1504].

Hashimoto, Yuko; Mizuno, Utako; Matsuoka, Hideki; Miyahara, Takafumi; Takakura, Masahiro; Yoshimoto, Mamoru; Oshima, Koichiro; Utimoto, and Kiitiro; Matsubara, Seijiro

doi:10.1021/ja015152o

Cited by 6 publications

(3 citation statements)

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“…Intramolecular cyclizations have also been achieved using Ti(II) reagents. 6−8 Among many other organic reactions, Ti(II) systems have been also implicated in enantioselective pinacol coupling reactions, 9,10 and in N 2 activation and N-atom transformations resulting in N-heterocycles. 11−13 Other ill defined sources of Ti(II) include [TiCl 2 (THF) n ], 4,14−16 [TiCl 2 (NCMe) 4 ], 17 or mixed-valent titanium reagents.…”

Section: Titanium(ii) Systems Have Been Indispensable In Organic Syntmentioning

confidence: 99%

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

et al. 2015

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A facile and high-yielding protocol to the known Ti(II) complex trans-[(py)4TiCl2] (py = pyridine) has been developed. Its electronic structure has been probed experimentally using magnetic susceptibility, magnetic circular dichroism, and high-frequency and high-field electron paramagnetic resonance spectroscopies in conjunction with ligand-field theory and computational methods (density functional theory and ab initio methods). These studies demonstrated that trans-[(py)4TiCl2] has a (3)Eg ground state (dxy(1)dxz,yz(1) orbital occupancy), which, as a result of spin–orbit coupling, yields a ground-state spinor doublet that is EPR active, a first excited-state doublet at ∼60 cm(–1), and two next excited states at ∼120 cm(–1). Reactivity studies with various unsaturated substrates are also presented in this study, which show that the Ti(II) center allows oxidative addition likely via formation of [Ti(η(2)-R2E2)Cl2(py)n] E = C, N intermediates. A new Ti(IV) compound, mer-[(py)3(η(2)-Ph2C2)TiCl2], was prepared by reaction with Ph2C2, along with the previously reported complex trans-(py)3Ti═NPh(Cl)2, from reaction with Ph2N2. Reaction with Ph2CN2 also yielded a new dinuclear Ti(IV) complex, [(py)2(Cl)2Ti(μ2:η(2)-N2CPh2)2Ti(Cl)2], in which the two Ti(IV) ions are inequivalently coordinated. Reaction with cyclooctatetraene (COT) yielded a new Ti(III) complex, [(py)2Ti(η(8)-COT)Cl], which is a rare example of a mononuclear “piano-stool” titanium complex. The complex trans-[(py)4TiCl2] has thus been shown to be synthetically accessible, have an interesting electronic structure, and be reactive toward oxidation chemistry.

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Section: Titanium(ii) Systems Have Been Indispensable In Organic Syntmentioning

confidence: 99%

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

et al. 2015

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“…This combined with the X-ray structure of the titanium-amine complex available in the literature led them to conclude that two species were present: one of them being a cluster of the TiCl 2 -227 and the other being a monomeric species with coordinated THF. It seems that the cluster leads to lower ee's: addition of tetrahydrothiophene resulted in higher selectivity (58% ee) [158]. Enders has used SMP, 228, under similar condi-Scheme 59 Pinacol coupling using titanium catalysts tions with low yields and moderate ee's (entry 4) [159].…”

Section: Pinacol Couplingmentioning

confidence: 99%

Enantioselective Radical Reactions

Zimmerman

Sibi

2006

Radicals in Synthesis I

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“…Pinacol coupling of benzaldehyde with TiCl 2 in THF in the presence of TMEDA gave the dl-hydroxybenzoin with high diastereoselectivity; by using an optically active amine in place of TMEDA, the homogeneous reaction afforded the product with 40% ee [236,237]. Similar reaction of benzaldehyde with TiCl 2 in the presence of two equivalents of (S)-2-methoxymethyl-pyrrolidine generates the diol with an enantiomeric excess of 65% [238].…”

Section: Effect Of Additives On the Ticl 4 -And Ticl 3 -Reducing Agenmentioning

confidence: 99%

The McMurry Coupling and Related Reactions

Ephritikhine

Villiers

2003

Modern Carbonyl Olefination

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Structural Studies of the Low-Valent Titanium “Solution”: What Goes on in the Pinacol Coupling Reaction? [J. Am. Chem. Soc. 2001, 123, 1503−1504].

Cited by 6 publications

References 0 publications

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

Enantioselective Radical Reactions

The McMurry Coupling and Related Reactions

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