“…Alkali-catalyzed rearrangements of 1,3-thiazines to 2thiopyrimidines are known. 20 Treatment of la with excess S-ethylthiuronium bromide in ethanolic sodium ethoxide afforded a crystalline product with the following characteristics. The UV spectral behavior was similar to that of isocytosine, but different from that of 2-alkylthiouracil.21 The IR spectrum of the product showed the presence of a CN group (2190 cm-1).…”