Stereoselective Addition of Organotitanium Reagents to Carbonyl Compounds

Reetz, Manfred T.; Steinbach, Rainer; Westermann, Jürgen; Peter, Roland; Wenderoth, Bernd

doi:10.1002/cber.19851180413

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Stereoselective Addition of Organotitanium Reagents to Carbonyl Compounds

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Reetz, M. T., Steinbach, R., Westermann, J., Peter, R., & Wenderoth, B. (1985). Stereoselective Addition of Organotitanium Reagents to Carbonyl Compounds. Chemische Berichte, 118(4), 1441-1454. doi:10.1002/cber.19851180413.

Cite as: https://hdl.handle.net/21.11116/0000-000E-7E6F-A

Abstract

Titanation of alkyllithium or -magnesium compounds using ClTi(OR)₃ results in reagents which show markedly increased diastereofacial selectivity (80–90%) in reactions with α-chiral aldehydes or ketones. Titanation is also the method of choice in Grignard-type additions to substituted cyclohexanones; CH₃Ti(OCHMe₂)₃ (6a) adds predominantly from the equatorial direction, while allyltitanium reagents 11b and 12 show axial preference. Crotyltitanium compounds react with carbonyl compounds to afford primarily adducts having anti-configuration, a process which is of particular value in case of ketones (anti/syn ratios up to 99:1). Titanation of (trimethylsilyl)allyllithium (48) with Ti(OCHMe₂)₄ reverses regioselectivity in reactions with aldehydes and ketones, β-hydroxy silanes 50 being the only observed products. These have anti-configuration and can be converted either into Z- or E-dienes using the Peterson elimination under basic or acidic conditions, respectively.