Wittig reactions phase transfer catalyzed

In conclusion, phase transfer catalyzed Williamson etherification and Wittig vinylation provided convenient methods for the synthesis of polyaromatics with terminal or pendant styrene-type vinyl groups. Both these polyaromatics appear to be a very promising class of thermally reactive oligomers which can be used to tailor the physical properties of the thermally obtained networks. Research is in progress in order to further elucidate the thermal polymerization mechanism and to exploit the thermodynamic reversibility of this curing reaction. 

A side reaction has been identified in the phase transfer catalyzed Wittig reactions. Hydroxide ion attacks positively charged phosphorus to give a phosphine oxide and the methylaromatic hydrocarbon from cleavage of the benzylic carbon-phosphorus bond (Equation 1). The phosphonium ion derived from 9-chloromethy anthracene... 

The use of polymers in phase transfer catalyzed Wittig reactions was first reported by Hodge and coworkers (Ref, 46) in 1980,... 

Catalyzed Wittig reactions. Wittig reactions of cyclopropylidenetriphenyl-phosphorane with carbonyl compounds proceed in low yield under standard conditions. Reactions conducted at 62° in THF with 1 (10 mole %) as the phase-transfer catalyst result in alkylidenecyclopropanes in 60-95% yield. ... 

These phosphines are typically used as ligands for catalytic reactions such as hydroformylation, hydrogenation, dimerization, and other metal-catalyzed reactions. Other uses for the phosphorus derivatives are Wittig chemistry (vitamin A and E), phase-transfer catalysis, epoxy curing, extractants, and agricultural and pharmaceutical intermediates. 

An interesting feature of the phase transfer Wittig reaction is that it succeeds in the absence of any added catalyst. Apparently, the phosphonium salts which are reactants in this system are also effective as phase transfer agents. It is less apparent why certain phosphonates should show the ability to catalyze these reactions and this is discussed in Sect. 1.3. In the phosphonium salt case, proton transfer must occur at the interface followed by dissolution of the ylid in the organic medium where it then undergoes the normal Wittig reaction. 

The Wittig reaction wherein a phosphonate is substituted for the more traditional phosphonium salt is called either the Wittig-Horner [8] or Wittig-Emmons [9] reaction. The synthesis of alkenes via base catalyzed phosphonate addition to an aldehyde or ketone has been accomplished under phase transfer conditions [10—13]. 

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