Redox-Neutral 1,3-Diol Synthesis by Base-Promoted Diastereoselective Alcohol-Aldolization
In order to prepare more efficiently key 1,3-diol fragments, we have devised a base-promoted redox-neutral condensation of ketones with alcohols. This diastereoselective alcohol-aldolization enables bypassing the classical oxidation and reduction steps necessary for the preparation of this crucial backbone by an overall redox-neutral formal borrowing hydrogen process. The starting alcohols constitute both the precursors of the in situ generated reactive aldehydes and the hydride source necessary for the chemoselective reduction of the aldol adduct intermediates.
MECHANISMS OF FREE-RADICAL REACTIONS. XX. REACTIVITY IN THE FREE-RADICAL HALOGENATION REACTIONS OF ARYLFLUOROALKANES
The free-radical chlorination and bromination of meta- and para-substituted benzyl fluorides and 1,1-difluoro-2-phenylethane and also the chlorination of 1-fluoro-2-arylethanes by phenylchloroiodonium chloride and the bromination of meta- and para-substituted benzyl bromides were studied by the method of competing reactions.In all cases a good correlation is observed between log krel and the Brown ?+ constants.In cases where change in the reactivity in the transition from one reaction series to another is due mainly to the polar effect of the substituent whilethe selectivity is measured in relation to the polar effect direct relationships are observed between the reactivity and the selectivity.
Dneprovskii, A. S.,Eliseenkov, E. V.
p. 711 - 719
(2007/10/02)
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