Trapped Intermediate of a Meerwein-Pondorf-Verley Reduction of Hydroxy Benzaldehyde to a Dialkoxide by Titanium Alkoxides.

Author(s) Boyle, T.J.; Guerrero, F.; Alam, T.M.; Dunnigan, K.A.; Sears, J.M.; Wheeler, D.R.
Journal Inorg Chem
Date Published 2020 Jan 06

A series of titanium alkoxides ([Ti(OR)] (OR = OCH(CH) (OPr), OC(CH) (OBu), and OCHC(CH) (ONep)) were modified with a set of substituted hydroxyl-benzaldehydes in pyridine (py). Instead of the expected simple substitution, each of the HO-BzA-L modifiers were reduced to their respective diol [(py)(OR)Ti(κ(O,μ-O')(OCH(CHO)-2)(L)] (OR = OPr, = 1, L = H (), OMe-3 (), Br-5 (·py), NO-5 (·4py); = 2, Bu-3,5 (), I-3,5 (), ONep; = 1, L = H (), OMe-3 (), Br-5 (·py), NO-5 (); = 2, Bu-3,5 (), I-3,5 (·py)), as identified by single crystal X-ray studies. The H NMR spectral data were complex at room temperature but simplified at high temperatures (70 °C). Diffusion ordered spectroscopy (DOSY) NMR experiments indicated that maintained the dinuclear structure in a solution independent of the temperature, whereas appears to be monomeric over the same temperature range. On the basis of additional NMR studies, the mechanism of the reduction of the HO-BzA-L to the dioxide ligand was thought to occur by a Meerwein-Pondorf-Verley (MPV) mechanism. The structures of - appear to be the intermediate dioxide products of the MPV reduction, which became "trapped" by the Lewis basic solvate.

DOI 10.1021/acs.inorgchem.9b03134
ISSN 1520-510X
Citation Inorg Chem. 2020;59(1):880890.

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