A new generation of "instant ylides": powder mixtures of phosphonium salts and potassium hydride as storable precursors to Wittig reagents
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After treatment with an appropriate base (butyllithium or sodium amide), 2-alkenyltris(2-methoxymethoxyphenyl)phosphonium salts carrying an allyl, crotyl, or prenyl (3-methyl-2-butenyl) side chain condense with satd. or unsatd. aldehydes to give conjugated ...
The key step in the trans-selective modification of the Wittig reaction is the a-lithiation of the lithium bromide coordinated ylide-aldehyde adduct (the so-called "P-betaine"). The olefination reactions were carried out for RCHO and [R1CH2PPh3]Br (R = C ...
The facile synthesis of five reagents (Cs+ and Ph3C+ salts) to introduce weakly coordinating anions (WCAs) Al(ORF)4- (ORF: OC(H)(CF3)2; OC(CF3)3) or lithium bridged {(RFO)2Al(m-ORF)2(m-Li)(m-ORF)2Al(ORF)2}- (Ph3C+ salt, ORF: OC(H)(CF3)2) is presented. All ...
Tris(2-methoxymethoxyphenyl)phosphine was readily quaternized when treated with Me bromoacetate. The resulting phosphornium salt was deprotonated to give the corresponding ylide (2-MeOCH2OC6H4)3P+CH-CO2Me (I). I reacted with satd., unsatd., or a-alkoxy sub ...
Stilbene type olefins can be prepd. with cis-stereoselectivities approaching 95:5 if tris(2-methoxymethoxyphenyl)phosphine derived ylides are employed and the reaction is carried out at -75 Deg. Thus, treating phosphonium ylide I with p-MeOC6H4CHO in THF c ...
The stereoselectivity of the SCOOPY reaction, in which allyl alc. derivs. are prepd. by reaction of betaine ylides with carbonyl compds., was investigated by the synthesis of 1-hydroxy-2-octene (I), and 1-hydroxymethyl-2-octene (II) from Ph3P+-CH2 and Ph3P ...
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)] ...
Phosphorus ylides combine with carbonyl compds. to give zwitterionic betaines as detectable intermediates of the Wittig reaction, provided that the neg. charge on the O atom was substantially reduced by binding to a Li cation or resonance delocalization in ...
