4.5- Dihydro-l,3-thiazoles. oxidation

Diese Ausbeute wird nur bei sorgfaltiger Temperaturkontrolle erreicht. 3,5-Bis-f4-methyl-phenyl]-2H-l,4-thiazin wird mit Palladium/Kohle (10%) in Atha-nol, dann unter Zusatz von Platin(IV)-oxid in Athanol zum 2-Methyl-2,4-bis-[4-methyl-phenyf]-2,5-dihydro-1,3-thiazol (92% d.Th.) unter Ringverengung hydriert2 ... 

A general scheme, which constructs the thiazolo variety of various bridgehead heterocycles, is basically an extension of HTIB-mediated modification of Hantzsch thiazole synthesis (Scheme 51). Thus, synthesis of 3-substituted-5,6-dihydro-4//-imidazo[2,l-b]thiazoles 202 has been achieved by the treatment of a-tosyloxyacetophenones (generated by the oxidation of 51 with HTIB) with ethylenethiourea [92JCS(P1)707], The method is successfully extended to synthesize 4,5,6,7-tetrahydrothiazolo[3,2-a]pyrimidines 203... 

Aryl-l,2,4-triazin-5(2//)ones react with indoles, pyrroles, pyrazoles and thiazoles in boiling butanol, and some other solvents, to give addition products e.g. 62. Oxidation results in aromatization <97JHC1013>. They also react with phenols and dialkylanilines to give 6-aryi-l,6-dihydro-l,2,4-triazin-5(2//)ones <97JHC573>. 

---