Phenylsulfonyl-2-trimethylsilylethylene

The somewhat low reactivity of ( )-phenylsulfonyl-2-trimethylsilylethylene in Diels-Alder reactions is probably due to steric hindrance exerted by both substituents and by the poor activation imparted by the silyl group. This drawback is partially offset by the effective elimination to the alkene performed under very irdld conditions with fluoride ion. The low dienophilic reactivity of the title reagent is evident in the reaction with isodicy-clopentadiene, for which it was demonstrated that only the isomer arising from the [l,5]-hydrogen sigmatropic shift was captured by dienophiles of low reactivity. Flighly reactive dienophiles react 

---

Cycloadditions. The dienophilic properties of ( )-phenylsulfonyl-2-trimethylsilylethylene allow the preparation of adducts with reactive dienes such as cyclopentadiene and... 

Article previously published in the electronic Encyclopedia of Reagents for Orgenic Synthesis as (E)-l-Phenylsulfonyl-2-trimethylsilylethylene. DOI 10.1002/047084289X. rpll9. 

Addition Reactions. The utility of ( )-phenylsulfonyl-2-trimethylsilylethylene in the synthesis of a-substituted allylsilanes is exemplified in eq 3 for y-hydroxyvinylsilanes, and in eq 4 in the preparation of isoprenoid structures. In these reactions the reagent functions as a Michael acceptor, but a-lithiation may compete with less nucleophilic bases such as butyllithium ... 

Radical Addition Reactions of Vinyltrimethylsilane. Reaction of the title reagent with benzenesulfonyl chloride under radical addition conditions provides ( )-l-phenylsulfonyl-2-trimethylsilylethylene (15), an acetylene equivalent in Diels-Alder reactions (eq 8). In similar fashion, thiophenol adds to vinyltrimethylsilane regioselectively.i Oxidation of the thiophe-... 

Analogous Reagents. 1 -Phenylsulfiny 1-1 -trimethylsilylethy-lene (1) and 1-phenylsulfonyl-l-trimethylsilylethylene (2) are used as synthetic analogs of 1-phenylthio-l-trimethylsilyl-ethylene. The sulfoxide (1) is an electron-deficient alkene so it... 

---