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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) ...
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 ...
A review of kinetic control in the diastereogenic formation of C-C bonds, Diels-Alder reactions, [2 + 2] cyclodimerization of olefins, syn preference in the formation of cyclopropanes from olefins and monosubstituted carbenes, reactions of organometallics ...
cf. CA 50, 10030g. The stationary ligands on the P were varied in order to obtain an insight into the mechanism of the carbonyl-olefination with triphenylphosphylenes. The results demonstrated that the substitution of the Ph by p-MeC6H4, p-MeOC6H4, piperid ...
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)] ...
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 ...
