Thiadiazoles and selenadiazoles

Activity continues in the investigation of all four isomeric series of thiadiazoles, and an increased interest in the selenadiazole analogues is discernible. The material is presented in the sequence established in the previous Reports. 

Reaction of [l,2,3]selenadiazole 281 with tetrakis(triphenylphosphine)platinum leads to the formation of a novel selenoplatinum catalyst 283 05TL1001 . This complex has been used as a catalyst for the hydrosilylation of terminal alkynes. Both 3,3-dimethylbut-l-yne and trimethylsilylacetylene undergo regioselective and sterereoselective hydrosilylation with dimethylphenylsilane in the presence of 0.0002 mol% of 283 to afford (E)-285 in good yields. In the case of phenylacetylene, the hydrosilylation is regioselective however, the stereoselectivity is reduced to 5 1 (E Z). 

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Aspects of the earlier thiadiazole and selenadiazole chemistry have been previously reviewed (68AHC(9)107, 70RCR923, B-61MI42600). In this chapter the literature through 1981 is surveyed with emphasis on developments of the past 20 years. 

The primary site of attack in the reactions of the 1,2,5-thiadiazoles and selenadiazoles with lithium alkyls or Grignard reagents is usually at the ring sulfur or selenium (Scheme 2, path A) but attack on nitrogen (path B) or the ring carbon (path C) also occurs. yV-Phenyl-o-phenylenediamine is produced in the reaction of (1) and (2) with phenyllithium, probably via path B (55JCS1468). The driving force for this mode of addition could depend on the stable benzenoid character of the addition intermediate. 

Reviews have appeared on biologically active 1,2,5-thiadiazoles and their condensed derivatives, fused 1,2,5-thiadiazoles and selenadiazoles, 1,2,4-thiadiazoles, steroidal thiazoles, isothi-... 

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