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Report | Regular issue | Vol 20, No. 6, 1983, pp.1089-1097
Published online, 1st January, 1970
DOI: 10.3987/R-1983-06-1089
S-Phenscylation of 6-Methyl-4-oxo-2-thio-2,3-dihydro-4H-1,3-oxazine and the Ring Transformation of the S-Phenacylated Compound

Tadashi Sasaki, Eikoh Ito, and Koji Asai

*Faculty of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan

Abstract

1,3-Oxazine 1 reacted with phenacyl bromide in water using sodium hydroxide as a base to give S-phenacylated derivative 2, but the homogeneous conditions such as NaH in THF or NaOMe in methanol caused the base-induced cycloreversion of 1, resulting in the formation of thiocyanate 3. For the purpose of the intramolecular transformation to pyrimidine-fused heterocycle 11, 2 was treated with ammonia in refluxing ethanol, but gave amidamine 6 while 8 was obtained with ammonium acetate in refluxing acetic acid. Although the direct ring closure failed, the target 11 was finally synthesized by the cyclodehydration of ketamide 7 with phosphorus pentoxide at 250 °C.