Miscellaneous Four-Membered Rings

This year has seen a notable increase in the work being done under this category. A study of the gas-phase pyrolysis of silacyclobutanes has been made and the photoreaction of benzosilacyclobutane with aldehydes and ketones is reported to form 1 1 adducts, but not via a a-silaquinone methide.  

Ishikawa, D. Kovar, T. Fuchikama, K. Nishimura, M. Kumada, T. Higuchi, and 

A novel preparation of a 4-bromophosphetan (62) has been described it proceeds by the reaction of l-bromo-3,3-dimethylbut-l-ene with phenyl-phosphorous dichloride in the presence of aluminium chloride, and subsequent reduction of the oxide.  

The short-lived phosphene (63) yields the oxaphosphetan (64) upon [27T + 27r] cycloaddition with ajS-unsaturated ketones. The reaction of sodium phenylacetylide with tellurium metal forms a 1,3-ditelluretan and not, as had previously been reported, a 1,3-ditellurole.  

4-Di-t-butylsilabenzene has been generated by base-induced elimination from l,4-di-t-butyl-l-chloro-l-silacyclohexa-2,4-diene. It dimerizes to the 1,3- 

Couret, J. Escudie, J. Satge, J. D. Andriamizaka, and B. Saint-Roch, J. Organomet. Chem., 1979, 182, 9. 

Part I Thiophens and their Selenium and Tellurium Anaiogues 

Two short reviews on the pharmaceutical and other uses of thiophen derivatives have appeared. 

An increased activity in the field of the chemistry of thienothiophens and thienoisothiazoles can be noticed. Many new complex tricyclic systems have also been synthesized. 

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MISCELLANEOUS FLUORINATED NITROGEN HETEROGYGLIGS Two reviews (1981, 1990) include nitrogen heterocychcs not covered in the present survey (482,483). The 1990 review dealing with four-, five-, and six-membered ring heterocycHc compounds emphasizes biological properties (482). 

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