78074-90-5Relevant academic research and scientific papers
Stereoselective olefination of N-sulfonyl imines with stabilized phosphonium ylides for the synthesis of electron-deficient alkenes
Fang, Fan,Li, Yuan,Tian, Shi-Kai
supporting information; experimental part, p. 1084 - 1091 (2011/04/15)
An unprecedented protocol has been developed for thestereoselective synthesis of structurally diverse electron-deficient alkenes in moderate to excellent yields from readily accessible N-sulfonyl imines and stabilized phosphonium ylides. Significantly, the olefination reaction of N-sulfonylimines with nitrile-stabilized phosphonium ylides affords an array of α,β-unsaturated nitriles with high Z selectivity, and the reactions with ester-, amide-, and ketone-stabilized phosphonium ylides afford α,β-unsaturated esters, amides, and ketones with high E selectivity, respectively. Spectroscopic analysis of the reaction mixtures and trapping of the intermediates allow plausible mechanisms to be proposed. Initialimine/ylide addition leads to the formation of betaines that cyclize to form 1,2-azaphosphetanes that subsequently eliminate iminophosphoranes to yield alkenes. For the synthesis of electron-deficient 1,2-disubstituted alkenes, the presence of an electron-withdrawing group in the betaine allows rapid interconversion between its two diastereomers through proton transfer. The Z/E selectivity for alkene synthesis is determined by the different rates at which the two betaine diastereomers form the corresponding 1,2-azaphosphetane diastereomers. In contrast, the Z/E selectivity for the synthesis of electron-deficient trisubstituted alkenes originates from the diastereoselective addition of stabilized phosphonium ylides to N-sulfonyl imines.
SYNTHESIS OF THE DIACETATE OF 4-CHLORO-2-HYDROXYMETHYL-2-BUTEN-1-OL. A USEFUL SYNTHON IN THE CHEMISTRY OF THE ISOPRENE UNIT
Cereda, E.,Bellora, E.,Donetti, A.
, p. 4977 - 4980 (2007/10/02)
A versatile procedure for the synthesis of the diacetate of 4-chloro-2-hydroxymethyl-2-buten-1-ol, a precursor of the dihydroxyprenyl synthon, is described.Its application to the synthesis of an unusual metabolite of a prenyl-containing drug is illustrated.
