18600-43-6Relevant academic research and scientific papers
Phosphonium salts and aldehydes from the convenient, anhydrous reaction of aryl acetals and triphenylphosphine hydrobromide
Ramanathan, Mani,Hou, Duen-Ren
, p. 98 - 108 (2013/05/09)
The reactions of aryl acetals/ketals and triphenylphosphine hydrobromide gave the corresponding aldehydes/ketones and alkyl phosphonium bromides. This reaction was applied to convert acetals/ketals to the corresponding aldehydes/ketones under an anhydrous
Reaction des oxirannes avec la triphenylphosphine en milieu phenolique
Christol, Henri,Grelet, Danielle,Darvich, Mohammad Raouf,Fallouh, Fayez,Plenat, Francoise,Cristau, Henri-Jean
, p. 477 - 483 (2007/10/02)
A new access to the vinylphosphonium salts 4 is proposed, using the reaction of epoxides 1 with triphenylphosphine at 100 deg C in phenol.It succeeds very well for the unfunctional epoxides 1 : 2-monosubstituted and 2,3-disubstituted epoxides.In the case of arylepoxides and 2,2-disubstituted unfunctional epoxides, Wittig and " retro-Wittig " side-reactions decrease the yields in vinylphosphonium salts.The reaction of opening epoxides by triphenylphosphine takes place since 40 deg C and is regio and stereoselective.At 40 deg C, the reaction leads to the formation of β-hydroxy alkylphosphonium salts 3.
Low-temperature characterization of the intermediates in the Wittig reaction
Vedejs,Meier,Snoble
, p. 2823 - 2831 (2007/10/02)
Nonstabilized salt-free ylides react with aldehydes and nonhindered or strained ketones at -78°C to give oxaphosphetanes. The Wittig intermediates can be observed by 31P and 1H NMR techniques. In the presence of LiBr, betaine-lithium bromide adducts often precipitate from solution. The oxaphosphetane from PhCHO + CH2=PPh3 reacts rapidly with LiBr to give a betaine·LiBr adduct, and the corresponding salt Ph3P+CH2CHOHPh Br- reacts with KH at -40°C to form the oxaphosphetane. No salt-free betaine has been detected. Lithium bromide is shown to decrease cis selectivity (CH3CH=PPh3 + PhCH2CH2CHO) in the condensation step and not by oxaphosphetane equilibration. Oxaphosphetane reversal to ylide + aldehyde is confirmed for aryl aldehydes but not for aliphatic aldehydes or ketones according to three types of crossover experiments. Rationales for cis selectivity of aldehyde-ylide reactions are discussed. A "crisscrossed" cycloaddition rationale is proposed, aldehyde and ylide planes tilted toward an orthogonal arrangement to minimize steric interactions, to explain cis-alkene formation. Other transition-state geometries having carbonyl and ylide planes roughly parallel are considered more likely for trans-olefin formation or for Wittig reactions of ketones.
