By Cycloadditions involving Thiet 1,1-Dioxides

By Cycloadditions involving Thiet, -Dioxides. The 2-thiabicyclo[2,2,01-hexane system is accessible by cycloaddition of thiet 1,1-dioxide to suitable enamines, 2-methyl-l-dimethylaminoprop-l-ene, for example, giving (68), and diethylaminoprop-l-yne providing (69) after hydrolysis. The 

The dienophilicity of thiet 1,1-dioxide was utilized to synthesize (73) from tetracyclone, whilst it acted also as a good dipolarophile towards diazoalkanes, giving mixtures of 1-pyrazoline derivatives (74) and (75) in which the isomers (74) predominated, except in the cases of diazomethane and diazoethane, where (75) was the major isomer. Ethyl diazoacetate on the other hand gave the 2-pyrazoline (76). These compounds arc potentially useful for the synthesis of bicyclobutanes by sequential expulsion of nitrogen and sulphur, and thermolysis or photol3rsis of (74 = R = 

Ph) did in fact give 5,5-diphenyl-2-thiabicyclo[2,l,0]pentane 2,2-dioxide (77).  

Reactions.—Thietan 1-oxide is reduced more readily than thiolan 1-oxide by aqueous sodium hydrogen sulphite or iodide ion. This observation was rationalized in terms of mechanisms involving nucleophilic displacement of a hydroxy-group (formed by protonation at sulphinyl oxygen) at sulphur by bisulphite or iodide ion.  

Tamagaki, M. Mizuno, H. Yoshida, H. Hirota, and S. Oae, Bull. Chem. Soc. Japan, 

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