Isomerism phosphonium salt-phosphorane

Tellurophosphoranes, obtained through a transylidation reaction between tellurenyl halides and phosphoranes, react with aldehydes to give the expected vinylic tellurides as an E Z isomeric mixture (method a). One other methodology involves the treatment of equimolar amounts of phenyl tellurenyl bromide and phosphonium salts with t-BuOK followed by an aldehyde (method b). Under these lithium-salt-free conditions, (Z)-vinylic tellurides are the main products. ... 

Alternatively, phosphine imines 388 had been treated with various phenylacetyl chlorides 392 (method B). Surprisingly, phosphonium salts 393 were isolated with 25 to 97% yield, which could be deprotonated by means of a base to build up the corresponding phosphoranes 394 (66-89% yield). Upon heating to 90-130 °C nitriles 391 were formed in 25 to 60% yield. This outcome was explained by an initial extrusion of Ph3P=0 to generate ynamines 395. The consecutive isomerization delivered iminoketenes 390, which underwent usual iminoketene Claisen rearrangement to produce the nitriles 391 (Scheme 10.77). 

The phosphorane of the phosphonium salt (677) was reacted with p-car-boethoxybenzaldehyde (678) in butylene oxide to give the isomeric tetrahydronaphthalene derivatives (679) and (680). The trans compound (679), which is predominantly formed and is highly active in the antipapilloma test, was isolated in crystalline form from this isomer mixture. The pure cis compound (680), which has hardly any activity, was isolated from the mother liquor by repeated thin-layer chromatography or more productively by high-performance liquid chromatography. 

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