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Abstract:
The relative rates of the addition of CH3Ti(OCHMe2)3 to various aldehydes and ketones have been determined at room temperature. Aldehydes react faster than ketones by a factor of 5̃00. Steric factors are primarily responsible. The synthetically and mechanistically important observation hatα-alkoxy and aminoketones are more reactive than the heteroatom-free analogs has been put on a quantitative basis (krel = 10–30) and interpretated on the basis of chelation. The activation parameters of the addition of CH3Ti(OCHMe2)3 to heptanal depend profoundly on the solvent (THF or CH2Cl2). In all cases 2. order kinetics are observed. This also applies to the addition of the ethoxy-analog CH3Ti(OEt)3 in THF, but not to its reaction in CH2Cl2. Mechanistic implications are discussed.
