89091-87-2Relevant academic research and scientific papers
Opposite stereochemical effects exerted by CeCl3 and TiCl4 on the Lewis acid mediated reduction of α-alkyl-β-ketophosphine oxides with metallic hydrides: A highly stereoselective protocol for the synthesis of syn and anti α-alkyl-β-hydroxyphosphine oxides
Bartoli, Giuseppe,Bosco, Marcella,Dalpozzo, Renato,Marcantoni, Enrico,Sambri, Letizia
, p. 1941 - 1950 (2007/10/03)
A general, highly efficient methodology for obtaining both syn and anti α-hydroxyphosphine oxides by reduction of the corresponding α-ketophosphine oxides is described. The nature of the Lewis acid was found to be pivotal in determining the outcome of these reactions. Strongly chelating TiCl4 led to the anti isomer in high diastereoisomeric excess in noncoordinating solvents (CH2Cl2) at -78°C with BH3/py as reducing agent, while nonchelating CeCl3 gave a high excess of the syn isomer in coordinating solvents (THF) at the same temperature with LiBH4 as reducing agent. In the latter case, CeCl3 is essential in achieving high yields and stereoselectivity, since it allows the reaction to be performed at low temperatures. Otherwise, higher temperatures (0 °C) are required, which lower both yields and selectivities. Moreover, each step of the protocol for the synthesis of stereodefined disubstituted olefins from alkylphosphine oxides (Warren's modification of the Homer procedure) has been optimized, and the optimized procedure has been applied to the synthesis of muscalure, the pheromone of the domestic fly.
TiCl4 mediated LiBH4 reduction of β-ketophosphine oxides: A high stereoselective route to the synthesis of anti-β-hydroxyphosphine oxides
Bartoli, Giuseppe,Bosco, Marcella,Sambri, Letizia,Marcantoni, Enrico
, p. 7421 - 7424 (2007/10/03)
The reduction of an α-alkyl-β-ketophosphine oxide with LiBH4 in presence of a strong chelating agent, such as TiCl4, gives the corresponding β-hydroxyphosphine oxide in high yields and with high anti-diastereoselectivity independently from the size of both the α- and β-alkyl chains.
The Stereocontrolled Horner-Wittig Reaction: Synthesis of Disubstituted Alkenes
Buss, Antony D.,Warren, Stuart
, p. 2307 - 2326 (2007/10/02)
Addition of the lithium derivatives of phosphine oxides Ph2P(O)CH2R1 to aldehydes gives erythro adducts (11) with good stereoselectivity.Reduction of α-diphenylphosphinoyl ketones (12) gives threo adducts (11) with even better stereoselectivity.Purification by flash chromatography and/or crystallisation followed by elimination of Ph2PO2 gives pure Z- or E-alkenes with high material conversion.Explanations are offered for the stereoselectivities, conditions defined for full stereochemical control, and guidelines suggested for approaches to a given alkene.
TRANS ALKENES BY STEREOSELECTIVE REDUCTION OF α-Ph2PO KETONES: E-ISOSAFFROLE, E-ANETHOLE, AND FENICULIN
Buss, Antony D.,Mason, Ralph,Warren, Stuart
, p. 5293 - 5296 (2007/10/02)
Conditions are described for the stereoselective reduction of α-Ph2PO ketones and stereospecific elimination from the resulting threo Horner-Witting intermediates to give pure E-alkenes such as the title compounds.
