Reactions of Phosphonium Ylides

A detailed study of the Wittig reactions of novel semi-stabilised ylide (56) has appeared. Unlike other semi-stabilised ylides, which typically give mixtures of E- 

So-called tandem, domino or cascade reactions provide powerful tools for the 

Finally, Shah and Protasiewicz have reviewed what they term phospha-variations of the Wittig and aza-Wittig olefination reactions where a phospha-Wittig is one that uses phospha-ylides , such as phosphoranylidene-o -phos- 

The reaction between phosphorus ylides and elemental sulfur or selenium has been used to prepare chalcogen-containing heterocyclic species. For example. 

The crystal structures of two phosphonium aryloxides (100), produced by the protonation of the corresponding ylides, have been determined. The compounds contain unusually short C-H O hydrogen bonds.  

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Alkenes (olefins) from reaction of phosphonium ylides with aldehydes or ketones... 

Horner reactions of phosphonium ylide and phosphine oxide... 

As previously mentioned (Section III.A) the reaction of phosphonium ylides with elemental sulfur afforded thioaldehydes which, by addition of amines, yielded the corresponding thioamides237. Another application involved the reaction of cyanothioacetamide with a /J-thioxoketone to give a pyridine-2-thione217. 

Camuzat-Dedenis, B. Provot, O. Moskowitz, H. Mayrargue, J. Reaction of phosphonium ylides and aromatic nitriles under Lewis acid conditions and easy access to aryl-substituted a-methoxyacetophenones. Synthesis 1999, 1558-1560. 

The course of reaction of phosphonium ylides (2a) with sugars is unambiguous only when protected aldehydo or keto sugars are used, although the interaction of (methylthio)methylenetriphenylphospho-nium ylide with free sugars has been reported.8 Such ylides are usually obtained by treatment of the corresponding phosphonium salts with a suitable proton-acceptor, for example, phenyllithium9- or sodium... 

Reactions of Phosphonium Ylides. - 2.3.1 Reactions with Carbonyl Compounds. This year we are able to report several variations of the traditional Wittig olefination which employ the addition of catalysts to effect the reaction. For example, Lebel et al. have reported a new salt-free process for the methyl-enation of aldehydes, in which the phosphorane is generated in situ from triphenylphosphine and a diazo precursor with either a rhodium- or rhenium-based catalyst (Scheme 6). It was found that the most effective combination of catalyst and diazo-compound were Wilkinson s catalyst [RhCl(PPh3)3] and... 

Dialkylboron-substituted phosphonium ylides have been prepared by reaction of dialkylchloroboranes with alkylidenephosphoranes (equation 50). The reaction of phosphonium ylides with alkyldichloro-boranes leads to the formation of boron-bridged 1,3-bisylides (equation 51). ... 

McKenna, E. G., Walker, B. J. The mechanism and stereochemistry of Wittig reactions of phosphonium ylide-anions. Phosphorus, Sulfur Silicon Relat. Elem. 1990, 49-50, 445-448. 

In an attempt to increase the Wittig-type reactivity of amide derivatives the reaction of phosphonium ylides, e.g. (91), with thioimides, e.g. (92) and (93), has been investigated.49 Although the thio-Wittig reaction takes place, S-alkylation and oxidation-reduction occur in competition and reduce the usefulness of this reaction in synthesis. Further studies of the reactions of a-perfluoroacylalkylphosphonium salt (94),50.51 generated by... 

The reaction of the diazomethylenephosphorane (105) with Lewis acids has been investigated.54 Reaction of (105) with boron trifluoride-etherate gave (106), the first example of an a-diazoalkylborate. 1,2,4-Benzotrithins (108) have been synthesized in moderate to good yields by the reaction of alkylidene ylides with benzopentathiepin (107).55 The reaction of phosphonium ylides with phosphorus trichloride has been re-investigated and products characterized for the first time.5 Depending on the molar ratios of ylide to trichloride used the ylides (109) and (110) are formed (Scheme 7). 

Mixed phosphonium-iodonium ylides 432 represent a useful class of reagents that combine in one molecule the synthetic advantages of a phosphonium ylide and an iodonium salt. The preparation of the tetrafluoroborate derivatives 432 by the reaction of phosphonium ylides with (diacetoxyiodo)benzene in the presence of HBF4... 

Transfer of substituted aromatic groups from silicon to boron is an efficient synthetic pathway for the preparation of aryl-halogenoboranes and diarylhalogenoboranes with different aryl groups. Substitution reactions of Cbis(trimethylsilyl)amino]--tert-butyl chloroborane have been reported and the reaction of phosphonium ylides with alkyldlchloroboranes investigated. ... 

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