ABSTRACT: 7-Benzyl-3-tert-butyl-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C22H25N3O, (I), and 3-tert-butyl-7-(4-methylbenzyl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H27N3O, (II), are isomorphous in the space group P2(1), and molecules are linked into chains by C-H...O hydrogen bonds. In each of 3-tert-butyl-7-(4-methoxybenzyl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H27N3O2, (III), which has cell dimensions rather similar to those of (I) and (II), also in P2(1), and 3-tert-butyl-1-phenyl-7-[4-(trifluoromethyl)benzyl]-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H24F3N3O, (IV), there are no direction-specific interactions between the molecules. In 3-tert-butyl-7-(4-nitrobenzyl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C22H24N4O3
