Steric effects thietane

The steric effect generated by the gem-dimethyl group of the thietane ring on the adjacent sp2 carbon atom makes the cycloaddition in these cases more sluggish compared with those of the parent thietane dioxide (6b)190. These cycloadditions provide a convenient entry into the strained thiabicyclo [2.2.0] hexane system (e.g. 287, 288 equation 107). 

The steric effects and rate constants for the reaction of cyclic sulfides, such as thietane with chloramine I (H3CC6H4NCl"Na ), in which the sulfides are converted to sulfimides and sulfoxides, have been investigated. ... 

Photoinduced cyclizations of phenyl triphenylsilyl thioketone (156) with cis- and fraws-l,2-dichloroethene give a mixture of silyl thietanes 157 and 158 in a regio- and stereoselective manner (equation 66)207. These reactions involving biradical intermediates and ring closure are governed by the steric effect. The steric hindrance between the Ph3Si group and the vicinal chlorine atom ensures their trans relationship in the thietane products. 

---