Rings with Nitrogen and Oxygen

Rings with Nitrogen and Oxygen.—The n.m.r. spectra of cis- and trans-A,5-diphenyl-, -4-methyl-5-phenyl-, and -3,4-dimethyl-5-phenyl-2-oxazolidones (34) have been interpreted in terms of ring conformations.  

bandshapes and dipole-moment measurements were used by Katritzky s group to study the conformations of tetrahydro-1,3- (35) and tetrahydro-1,2-oxazines (36) as well as of tetrahydro-1,3-thiazine (37) and 1-t-butylhexa-hydropyrimidine (38). Compounds (35), (37), and (38) have an axial NH 

study of the conformational equilibria is cis- and trans-2,3-diphenyl, 3-methyl-2-phenyl-, and 3,4-dimethyl-2-phenyl-morpholines (39) and the related 5-oxomorpholines shows that these series of compounds prefer chair (40) and half-chair (41) conformations, respectively.  

The Prins reaction of a tenfold or larger excess of formaldehyde with 1-substituted 4-phenyl-l,2,3,6-tetrahydropyridines gives the bicyclic compound (42), 2 which exists in the 0-inside conformation as previous work had suggested should be the case. 

The preparation and n.m.r. spectra of a series of hexahydropyrido[2,l-c]-[1,4]oxazin-4(3JT)-ones (43) have been reported. Configurations and conformations are assigned on the basis of n.m.r. measurements. The predominant conformation is shown to be that with the ring oxygen atom and angular hydrogen atom on the same side of the C3—C(0)—plane. 

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Formation of six-membered rings with nitrogen and oxygen or sulfur atoms. Almost all the papers on the transformations of isatoic anhydrides leading to the formation of new six-membered rings with two different heteroatoms have been devoted to the synthesis of derivatives of 3,1-benzoxazine. There is only one paper in which the production of a derivative of 3,1-benzothiazine is described. 

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