Oxazepin

Irradiation of the fused ring isoxazoline (27) gave the ring expanded product, oxazepine (28), in 80% yield. 

Chamicel Name 2-Chloro-11-(1-piperazinyl)dibenz[b,f] [1,4] oxazepine... 

A mixture of 10 g of the above piperazine carboxylate ester, 8 g of phosphorus pentoxide and 20 ml of phosphorus oxychloride is heated under reflux for about 1 day, diluted with 100 ml each of chloroform and benzene and quenched with 200 g of ice. The mixture is made basic with 10% sodium hydroxide. Theorganic layer is Isolated and extracted with 150 ml of dilute hydrochloric acid. The product is precipitated from the aqueous layer by addition of 10% sodium hydroxide, extracted with benzene and dried over potassium carbonate. Recrystallization from benzene-petroleum ether gives 2[Pg.77]

This crude product is dissolved in 100 ml of dilute hydrochloric acid, the acid solution is extracted with ether, and the aqueous layer is made basic with sodium hydroxide solution (3N) in the presence of ether (approximately 250 ml). The ether layer Is separated, dried over potassium hydroxide and evaporated to a white solid. Additional purification by repeating the formation of the hydrochloric acid salt and reprecipitation of the base is carried out. When purified in this manner, followed by drying at 80°C in vacuo over phosphorus pentoxide, 2-chloro-11-(4-methyl-1-piperazinyl)dibenz[b,f] [1,4]oxazepine, li/IP 109° to 111°C, is obtained. 

No monocyclic 1,2-oxazepines have been reported, but annulated derivatives are known. 

The first reported derivative of 1,2-oxazepine was dibenz[f,/][l,2]oxazepine-ll-carbonitrile (3 a). This, together with small amounts of compounds 4 and 5, is formed when acridine-9-carbonitrile 10-oxide (la) is irradiated with UV light,6,7 It is likely that the reaction proceeds by way of the oxaziridine valence tautomer 2a, which, however, was not detected.7 Photo-isomcrization of 9-chloroacridine 10-oxide (lb) yields the 11-chlorodibenzoxazepine 3b.6,7... 

The action of lithium aluminum hydride on ll-chlorodibenz[c,/][l,2]oxazepine results in the formation of 2-(2-hydroxybenzyl)aniline (l).6... 

Treatment of dibcnz[e,/J[1,2]oxazepine-l 1-carbonitrile or 1 l-chlorodibenz[c,/][l,2]oxazepine with triphenylphosphane in acetonitrile at room temperature yields the acridines 5 quantitatively.7... 

Simple 1,3-oxazepines are rather unstable they have rarely been isolated. 

Oxazepine-2,4-dicarbonitrile (lb) and 6-methyl-l,3-oxazepine-2,4-dicarbonitrile (lc) are obtained from the corresponding pyridine oxides 9 both oxazepines decompose on attempted chromatography. 

Irradiation of an acetone solution of 2,4,6-triphenylpyridine 1-oxide results in an inseparable mixture of 2,4,6-triphcnylpyridinc (2) and 2,4,6-triphenyl-l,3-oxazepine (3).10... 

Stable tetra- and pentaaryl-l,3-oxazepines 4 are formed in good yield when the corresponding pyridine 1-oxides are irradiated the products are accompanied by small amounts of the... 

Irradiation of the unsymmetrically substituted 2,3,4,6-tetraphenylpyridine 1-oxide (5) under these conditions gives 2,4,6,7-tetraphenyl-l, 3-oxazepine (7) in 30 % yield, together with 2,4,5,6-tetraphenylpyridin-3-ol (10) in 37% yield and 2,3,4,6-tetraphenylpyridine (30%).11 It has been suggested that the reaction proceeds by way of the oxaziridines 6 (which yields 7) and 8 (which yields the isomeric oxazepine 9) the latter rearranges to the pyridinol 10. 

Another photochemical ring enlargement leading to a 1,3-oxazepine is the formation of 2-phenyl-l,3-oxazepine (13) by irradiation of 4-phenyl-2-oxa-3-azabicyclo[3.2.0]hepta-3,6-diene (11).12 It is proposed that the process involves the azirine 12 as an intermediate. 

Ethyl 2,4,7-triaryl-l,3-oxazepine-6-carboxylates 15 are formed in modest yield by the reaction of ethyl diazoacetate with 1,3-oxazinium perchlorates 14.13... 

Ethyl 2,4,7-Triphenyl-l,3-oxazepine-6-carboxylate (15a) Typical Procedure 13... 

The reaction of sodium azide with tri-, tetra- or pentaarylpyrylium salts 16 gives highly unstable 2-azido-2//-pyrans 17, which readily lose nitrogen to form 1,3-oxazepines 18 (see Houben-Weyl, Vol.E7b, p 983 ff) typical examples are listed.1415... 

In the case of 2,3,5,6-tetraphenylpyrylium perchlorate, the product is the oxoazirine 19, which rearranges to the oxazepine 20 in boiling xylene. 

Dimethyl-5-phenyl-l,4-oxazepine isomerizes to 6,7-dimethyl-4-phenyl-l,3-oxazepine in boiling benzene.30 The process involves successive valence isomerization, a walk rearrangement and a second valence isomerization. 

Oxazepines are readily decomposed by heat and light and by acids and bases.8 Some of these reactions proceed by hydrolytic opening of the oxazepine ring, as in the formation of 1-benzoylpyrrole (1) from 2-phenyl-l,3-oxazepine and cold dilute hydrochloric acid,12 while others involve valence-tautomeric oxazanorcaradienes, as in the thermal conversion of 2-phenyl-l,3-oxazcpine into 2-phenylpyridin-3-ol (2).12... 

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