Pyrido phenoxazines

Phenoxazinyl)propionic acid undergoes an interesting cycli-zation with phosphorus pentoxide, to give a mixture of the pyrido-phenoxazine (49) and the corresponding dihydroderivative (50).65,75... 

Golich, T. G., Eldrod, L. Jr. and Morley, J. A. Determination of minor impurities and diastereomers of 6-[3-[(2-amino-l-oxopentyl)amino]-l-pyrrolidinyl]-5-fluoro-3-oxo-3H-pyrido [3,2,l-kl]phenoxazine-2-carboxylic acid hydrochloride by high performance liquid chromatography. J. Liq. Chromatogr. 17 2005-2016, 1994. 

Heating benzoxazinone under the same conditions leads to 4,5,6-tetrafluoro-3f/-pyrido[3,2,l-k]phenoxazin-3-one (97ZOR1418) (Scheme 160). 

Hydroxypyridone ring synthesis. 80 g. phenothiazine, diethyl n-butylmalonate, and unglazed clay plate fragments heated 22 hrs. at 277° crude l-keto-2-n-butyl-3-hydroxy-lH-pyrido[3,2,l-kl]phenothiazine. Y 73%.—Clay plate catalyzes this reaction and particularly prevents decreasing yields of larger batches. F. e., also with phenoxazine, s. M. Harfenist et al., J. Org. Chem. 27, 3977 (1962). 

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