Thiane chlorination

Whereas a-chlori nation of sulfones usually constitutes a problem, thiane oxides are easily chlorinated at the a-position by a wide spectrum of chlorinating agents338. The mechanism is similar to that with carbonyl groups339. 

Detailed studies of the a-chlorination of substituted thian S-oxides have been published. This reaction also showed remarkable stereoselectivity, and the determination of the stereochemistry of the products has given valuable mechanistic information. Mcmochlorination of either cis- or trans-4-t-butylthian S-oxide gave the same products the major one, (44), formed in 95% yield, had the oxygen atom equatorial and the chlorine axial. The minor chlorination product (45) also had the chlorine atom and sulphur lone-pair trans . ... 

Cl atom become trans— led to (44). Product analysis of a variety of other thian S-oxides fully supported the above mechanism. o-Bromination of six-membered-ring sulphoxides proceeded similarly. Highly stereoselective CK-chlorinations have also been reported for five-membered-ring sulphoxides the major products resulted from trans -additicm to the intermediate oxosulphenium ion. A survey and discussion of the methods available for the assignment of configurati( is of cyclic sulphoxides has been made. Benzene-, trifluoroacetic acid-, and [Eu(d m)3]-induced shifts were shown to be most reliable. A comparison of the size of of the... 

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