Thiolactams dehydrogenation

OL, -Unsaturated thiolactams.2 Thiolactams can be dehydrogenated by reaction with this sulfinyl chloride followed by mild acid treatment (equation 1). The reaction may involve attack on sulfur, rather than carbon, followed by a 1,4-elimination. The generality of this dehydrogenation has not been established. It is useful for indirect dehydrogenation... 

Little woric has been carried out on sulfmylation reactions on those systems having thiocaibonyl and imino moieties. However, hydrazones are converted to a-sulfinyl derivatives on reaction of their anions (prepared from LDA in THF) at -78 C with sulrinate esters, although the full utility of this reaction remains to be explored. Furthermore, in an unusual reaction, p-toluenesulfmyl chloride has been shown to effect a facile one-step dehydrogenation of the thiolactam (17 equation 7) in good yield. These reactions contrast with the oxidative removal of thiocarbonyl, hydrazonyl and similar functionalities with Se species (see Section 2.2.4.2). 

NBS-suIphuric acid at 70-100 °C is an efficient reagent for the dehydrogenative cyclization of a substrate containing a thiolactam and a neighbouring benzene ring. A -Chlorosuccinimide-suIphuric acid may give better results on 6-thioxopyrazolo[3,4-i/]pyrimidin-4-one [3349]. 

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