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Paper | Regular issue | Vol 29, No. 9, 1989, pp.1735-1740
Published online, 1st January, 1970
DOI: 10.3987/COM-89-5036
Synthesis of Derivatives of 3,4-Dihydro-6H,8H-pyrimido[4,5-c][1,2]oxazin-7-one

P. Kong Thoo Lin and D. M. Brown

*MRC Labratorys of Molecular Biology, Hills Road, Cambridge, CB2 2QH, U.K.


In model experiments seeking a pyrimidine which had the hydrogen-bonding potential of both thymine and cytosine synthetic routes to the bicyclic 3,4-dihydro-6H,8H-pyrimido[4,5][1,2]oxazin-7-one 2 ring system have been investigated. 1-Methyl-5-(2-bromoefhyl)uracil 3 was converted to the 5-(2-phthalimido-oxyethyl) derivative 9 and then to the corresponding 4-triazolo derivative 10. Ammonia in dioxan afforded 6-methyl-3,4-dihydro-6H,8H-pyrimido[4,5-c][1,2]oxazin-7-one 11. The ring closure of 4-oxyimino-5-(2-chloroethyl)pyrimid-2-ones was also investigated, yielding 1,6-dimethyl- and 1-benzyl-6-methylpyrimido[4,5-c][1,2]oxazin-7-one, but not the parent structure 11.