Phenylvinyl sulfone

As pointed out in Section 7.4.1, the head-to-head cyclodimerization is typical for phenylvinyl ether cation-radical (see Scheme 7.19). The anion-radical of phenylvinyl sulfone undergoes the same dimerization. The reaction is initiated electrochemically, develops according to the chain mechanism, and also leads to the trans-cyclic product (Bergamini et al. 2004). 

The reaction also proceeds with a high degree of regiospecificity. In particular, treatment of 344 with methyl acrylate (R = COaMe), acrylonitrile (R = CN), and phenylvinyl sulfone (R = S02Ph) with Zn(II) as the metal salt, led in each case to the formation of a single regio- and stereoisomer (345) in 70, 87, and 80% yield, respectively (Scheme 3.117). 

Only a limited number of vinyl sulfones, e.g. phenyl ( )-2-phenylvinyl sulfone (14), undergo codimerization with MCR Homocyclodimerization of MCP is the most efficient side reaetion. Interestingly, yields and product distributions are solvent dependent. No reaction takes place with catalytic amounts of bis(t -cycloocta-l,5-diene)nickel(0)/triphenylphosphane. In this case the vinyl sulfones are strongly coordinated to the catalyst metal, thus preventing interaction with MCP. When the sulfones bear alkyl-substituted vinyl groups, isomerization to yield allyl sulfones usually proceeds faster than cycloaddition, at least in the case of palladium(O) catalysis. 

An improved synthesis of eletriptan (20) was achieved starting from A-acykited indole 19 (A-protected to avoid addition across the double bond) with phenylvinyl sulfone via the Heck reaction [79a,b]. Substituted indole 20 is a potent serotonin (5-IIT ) agonist and may be used in the treatment of depression, anxiety, etc. 

Nucleophilic addition of pyrroles to phenylvinyl sulfone successfully proceeds at higher concentration of KOH (equimolar amount) and the increased reaction time (Scheme 2.26, Table 2.2) [443]. 

The acid cleavage of a-phenylvinyl diethyl phosphate, which most probably proceeds by an ASj 2 mechanism, was found to be catalyzed by micellar sodium dodecyl sulfate (NaLS) and hexadecyl sulfonic acid (Table 8), whereas that of phosphoenol pyruvic acid was slightly inhibited by cationic and anionic surfactants (Bunton and Robinson, 1969c). The considerably greater rate enhancement by sodium dodecyl sulfate in 0-01m than in 0-10 m acid (Table 8) can reasonably be attributed... 

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