Four-membered Rings containing Sulphur and Oxygen

10 Four-membered Rings containing Sulphur and Oxygen 

Calculations concerning the stabilities of 1,2-oxathietan 2-oxide, 1,2-oxathietan-3-one and its enol, and 1,2,3- and 1,3,2-dioxathietans have appeared. 

The anhydride (126) has been prepared at 10 K by photochemical addition of SO2 to keten. It decomposes photochemically to formaldehyde, COj, and sulphur. The reaction of the tetramethylcyclobutadiene-AlClj complex with SOj gives a new complex, which might be (127).  

The reaction of two derivatives of 5,5-diallylbarbituric acid with sulphuric acid in acetonitrile is said to give characterizable 6-sultones. Addition of SO3 to hexafluorobutadiene occurs in a 1,2 manner to give (128). The double bond of (128) can be brominated to give another stable -sultone. The addition is reversible above 20 °C, and (128) reacts with excess SO3 to give (129) and SOj.  

Oxathietan 1,1-dioxide (130) reacts with alcohols to give (2-fluorosulphonyl)-carboxylic esters, and with BFj and EtjN to give fluorosulphonyl(trifluoro-methyl)keten. The latter reaction is more efficient if the ring is first opened with KF and HF. Chloral cyclo-adds to sulphenes to give yff-sultones. 4-Tri-chloromethyl-l,2-oxathietan 2,2-dioxide reacts with primary and secondary amines to give y5-hydroxy-sulphonamides.  

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