71962-02-2Relevant academic research and scientific papers
Highly trans-selective intramolecular pinacol coupling of dials catalyzed by bulky Cp2TiPh
Yamamoto, Yoshihiko,Hattori, Reiko,Itoh, Kenji
, p. 825 - 826 (1999)
Cp2Ti(Ph)Cl in the presence of Me3SiCl and Zn provides an effective pinacol coupling catalyst for aromatic and aliphatic aldehydes.
Chemoselective Pd-catalyzed oxidation of polyols: Synthetic scope and mechanistic studies
Chung, Kevin,Banik, Steven M.,De Crisci, Antonio G.,Pearson, David M.,Blake, Timothy R.,Olsson, Johan V.,Ingram, Andrew J.,Zare, Richard N.,Waymouth, Robert M.
supporting information, p. 7593 - 7602 (2013/07/05)
The regio- and chemoselective oxidation of unprotected vicinal polyols with [(neocuproine)Pd(OAc)]2(OTf)2 (1) (neocuproine = 2,9-dimethyl-1,10-phenanthroline) occurs readily under mild reaction conditions to generate α-hydroxy ketones. The oxidation of vicinal diols is both faster and more selective than the oxidation of primary and secondary alcohols; vicinal 1,2-diols are oxidized selectively to hydroxy ketones, whereas primary alcohols are oxidized in preference to secondary alcohols. Oxidative lactonization of 1,5-diols yields cyclic lactones. Catalyst loadings as low as 0.12 mol % in oxidation reactions on a 10 g scale can be used. The exquisite selectivity of this catalyst system is evident in the chemoselective and stereospecific oxidation of the polyol (S,S)-1,2,3,4-tetrahydroxybutane [(S,S)-threitol] to (S)-erythrulose. Mechanistic, kinetic, and theoretical studies revealed that the rate laws for the oxidation of primary and secondary alcohols differ from those of diols. Density functional theory calculations support the conclusion that β-hydride elimination to give hydroxy ketones is product-determining for the oxidation of vicinal diols, whereas for primary and secondary alcohols, pre-equilibria favoring primary alkoxides are product-determining. In situ desorption electrospray ionization mass spectrometry (DESI-MS) revealed several key intermediates in the proposed catalytic cycle.
Diastereoselective inter- and intramolecular pinacol coupling of aldehydes promoted by monomeric titanocene(III) complex Cp2TiPh
Yamamoto,Hattori,Miwa,Nakagai,Kubota,Yamamoto,Okamoto,Itoh
, p. 3865 - 3870 (2007/10/03)
A monomeric titanocene(III) derivative, Cp2TiPh, effectively promoted the pinacol coupling of both an aromatic aldehyde, benzaldehyde, and an aliphatic aldehyde, 3-phenylpropionaldehyde. The same reactive complex was successfully generated by a catalytic amount of a precursor, Cp2Ti(Ph)Cl, and its stoichiometric amount of Zn. The Cp2TiPh-catalyzed pinacol coupling of benzaldehyde derivatives and aliphatic aldehydes afforded the corresponding 1,2-diols in high yields with moderate to good threo-selectivity. On the other hand, Cp2TiPh-catalyzed pinacol-cyclization of dials gave cyclic 1,2-diols with excellent diastereoselectivity. The extension of this protocol to chiral dials demonstrated that the phenyltitanium complex catalytically transmitted an axial chirality or a central, chirality of the starting dials to the central chirality of the resultant 1,2-diols.
Stereoselectivity in the Epoxide Hydrase Catalyzed Hydrolysis of the Stereoisomeric 4-tert-Butyl-1,2-epoxycyclohexanes
Bellucci, Giuseppe,Berti, Giancarlo,Ingrosso, Giovanni,Mastrorilli, Ettore
, p. 299 - 303 (2007/10/02)
The steric course of the rabbit liver microsome promoted hydrolysis of the racemic cis and trans forms of the title epoxide was investigated. The (+) and (-) forms of c-4-tert-butylcyclohexane-r-1,t-2-diol were the only hydrolysis products, indicating that the enzyme reaction takes place exclusively by diaxial opening of the oxirane ring.The absolute configuration and maximum rotation of this diol were determined by correlation with (1S,3R)-cis-3-tert-butylcyclohexanol.Of the four stereoisomers of the epoxide, the (1S,2R,4S) form was by far the best substrate and the (1R,2S,4S) form the worst.At low conversion, high enantiomeric excesses of the (-)-diol and the (+)-diol were obtained, respectively, from the (+/-)-trans and the (+/-)-cis epoxide; optical purities decreased with increasing conversion.The results are discussed in terms of the helicity of the cyclohexane ring and of the orientation of the tert-butyl group with respect to the oxirane ring.
