42009-13-2Relevant academic research and scientific papers
A novel double olefination. Highly stereoselective synthesis of trifluoromethylated 1,3-butadienylphosphonates
Shen, Yanchang,Li, Ping,Ni, Jiahong,Sun, Jie
, p. 9396 - 9398 (1998)
The bisphosphoryl-stabilized carbanion (2), generated from tetraethyl ethyl-1,1-bisphosphonate (1) and n-butyllithium in tetrahydrofuran (THF), was acylated by the addition of trifluoroacetic anhydride to give trifluoroacylated bisphosphonate (3). Without isolation, 3 was reacted with [(diethylphosphinoyl)methyl]lithium, and elimination of phosphonic acid anion afforded 4. Treatment of 4 with LDA gave phosphoryl-stabilized carbanion 5, which in the reaction medium was able to react with aldehyde to give substituted trifluromethylated 1,3-butadienylphosphonates in 66-88% yields with the 1E,3E isomer exclusively or predominately. Thus, the double- olefination methodology provides a simple and convenient synthesis of the title compounds. The first example of crystallization of diethyl 1-methyl-2- trifluoromethyl-4-(4'-nitrophenyl)-1,3-butadienylphosphonate with 1,4- dinitrobenzene was obtained by a cocrystallization method. Hence, the configuration of the products could be ascertained on the basis of the crystal structure. A possible mechanism for the explanation of stereochemical results is proposed.
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.
