Wittig. thio

The first reliable evidence for the formation of thiabetaines (+)P-C-C-S( ) as true intermediates in thio-Wittig reaction was obtained11-13 only after the synthesis and complete characterization of the corresponding thiabetaines I of the silicon series.14,15 This evidence was based on the resemblance of the spectral parameters of compounds of both series.11... 

Tellurium sources, 22-24 Thermodynamics in cyclo-oligomerization, 185-186 butadiene insertion, 187-188 reductive elimination, 193, 194 selectivity control, 212 polysilane isomerisation, 158-160 see also Stability Thermolysis, 135, 136, 158 THF (tetrahydrofuran), 97, 150, 153 Thio-Wittig reaction, 37 Tin, 121... 

The thio-Wittig reaction, like the Wittig itself, may involve (thia)phosphetane or betaine-type structures as intermediates. A combined experimental and theoretical study over a wide range of conditions and of substrates (aliphatic vs aromatic, aldehyde- vs ketone-derived) suggests a mechanistic continuity, with solvent polarity and substrate electronic effects being the main influences on the transition from one mechanism to another. ... 

The thio-Wittig reaction between thioaldehyde and phosphorus ylides yields initially a thiaphosphetane, which undergoes cycloreversion to a P=S bond444. 

The lithium enolate formed from methyl S-trityl mercaptoacetate (8) has been C-alkylated in high yield at or below —40 °C (Scheme 4).37 At higher temperatures, the [ 1,2]-thio-Wittig rearrangement of the enolate was the predominant process. ESR evidence has indicated that the rearrangement occurred by a radical mechanism. 

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 [l,2]-thio-Wittig rearrangement has been examined by several groups, and is known for both simple thioethers and a-thiocarbonyl derivatives. In a representative transformation, deprotonation of ester 69 followed by warming to -40 °C led to [l,2]-thio-Wittig rearrangement. A 75% yield of 70 was obtained after a CH3I quench. ... 

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