1 -Thia-2-silacyclopentanes

Nucleophilic displacement on 1-chlorosilacyclopentanes is dominated by inversion, in contrast to silacyclobutanes (78JOM(154)203). For 2-oxa- and 2-thia-silacyclopentanes, however, both inversion and retention are observed. The stereochemistry is determined by the leaving group and the electronic nature of the nucleophile rather than ring strain... 

SCHEME 4. Optically active oxa- and thia-silacyclopentanes (after References 33 and 34)... 

Similarly, ring expansion of fused ring siliranes also occurs stepwise with silabicyclo[3.1.0]hexane and silabicyclo[4.1.0]heptane (equation 34). With 1,1-dimethyl-1-silacyclobutane, sulphur insertion occurs to give the l-thia-2-silacyclopentane in 72% yield67. 

A kinetic study was performed and thermodynamic factors were estimated for the activation energy of abstraction of hydrogen atoms from a disilacyclopentane <74izv6i>. In addition, a thermochemical study of the dissociative ionization of 2,3,3-trimethyl-l-thia-3-silacyclopentane has been reported <85JOM(288)27>. 

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