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A review, with 6 refs., of the prepn. of olefins from phosphonium ylides and carbonyl compds. and from phosphonium ylides, carbonyl compds., org. Li compds., and reactive halogen compds., such as MeCOCH2Cl and EtI. [on SciFinder (R)] ...
A review, with 91 refs., of stereoselectivity in reactions of stable and reactive ylids, and the application of stereoselective carbonyl olefinations. [on SciFinder (R)] ...
Primarily trans-olefination has been achieved by rapid equilibration of erythro- and threo-betaines. The betaine ylides (I) are formed by the treatment of betaine-LiX adduct with PhLi or n-BuLi in 1:1 ether-tetrahydrofuran at -30 Deg. The equil. between th ...
Reaction of Ph3P+C-HR with R1CHO at -78 Deg yielded Ph3P+CHRCHR1O- (I). Subsequent addn. of BuLi gave Ph3P+C-RCHR1O- Li+ (II). Reaction of II with HCl and hydrolysis with tert-BuOK gave .apprx.80% RCH:CHR1 (R = Et, Ph, or C5H11; R1 = Me, Et, or C5H11). Whe ...
Olefins of the formula R1XC:CR2R3 were prepd. by removal of a proton from a betaine-like intermediate, (Ph)3P+-CHR1CR2R3O-, and subsequent treatment with the desired X+. Thus, 1 mole PhLi and the phosphonium salt, (Ph)3PCH2R1.HCl, in 3 parts Et2O and 1 par ...
Alkylidenetriphenylphosphoranes (I) tend in general towards cis olefination. The proportion of cis olefin in the isomer mixt. is highest when the ylide used is salt-free. Li salts favor the formation of the trans isomers. Salt-free I and BzH in 4:1 C6H6-pe ...
H atoms in the a-position to a quadricovalent P atom could be exchanged by D with D2O under mild alk. conditions. The phosphonium salts, which can be readily deuterated under these conditions, served as the key intermediates for the synthesis of selectivel ...
Phosphorylide complexes, Li+[Ph3P+C-HR]X-, where R = H, alkyl, or alkoxy, gives very poor yields of olefins from aldehydes in the Wittig reaction. In the presence of 1.1 equivs. tert-BuOK the reaction is strongly accelerated. By this method methylenecycloh ...
Unstabilized P ylides and their betaines added Li salts, losing most of their reactivity, and were reactivated with tert-BuOK, making thus possible the retardation or the acceleration of the Wittig reaction. The C:O olefination often yielded an isomer mixt ...
Wittig reactions of the ylide (Ph3P+CH-)2CH2 (I) with aliphatic aldehydes and ketones are described. A soln. of I in THF prepd. from (Ph3P+CH2)2CH2.2Br- was treated with an equimolar amt. of geranylacetone to give a stereoisomeric mixt. of II (norsqualene) ...
