Dihydro structure

Isoxazolo[5,4-d]isoxazole, 3a,6a-dihydro-structure, 6, 975 synthesis, 6, 1018 Isoxazoloisoxazoles synthesis, 3, 41 Isoxazoio[2,3-h]isoxazoies synthesis, 6, 1001 Isoxazolo[4,5-d]isoxazoles synthesis, 6, 989, 997... 

Pteridine, 4,7-dichloro-2-methylthio-synthesis, 3, 296 Pteridine, 3,4-dihydro-structure, 3, 279 Pteridine, 5,6-dihydro-properties, 3, 306 Pteridine, 5,8-dihydro-structure, 3, 306 Pteridine, 7,8-dihydro-... 

Pteridine, 4-imino-1 -methyl-1,4-dihydro-basicity, 3, 270 Pteridine, 7-methoxy-synthesis, 3, 297 Pteridine, 2-methyl- H NMR, 3, 285 reactions, 3, 288 structure, 3, 266 Pteridine, 4-methyl-Gabriel s synthesis, 3, 309 H NMR, 3, 285 reactions, 3, 288 structure, 3, 266 Pteridine, 6-methyl-bromination, 3, 301 structure, 3, 266 synthesis, 3, 312 Pteridine, 7-methyl-aldol-type condensation, 3, 302 bromination, 3, 301 H NMR, 3, 285 structure, 3, 266 synthesis, 3, 312 Pteridine, 2-methylamino-solubility, 3, 271 Pteridine, 2-methyl-3,4-dihydro-striicture, 3, 279 Pteridine, 6-methyl-3,4-dihydro-structure, 3, 279... 

Pteridin-6-one, 7-methyl-7-(7-oxopteridin-6-ylmethyl)-7,8-dihydro-structure, 3, 283 Pteridin-6-one, 7-morpholino-synthesis, 3, 317... 

In the ring-closure reaction of a-acylaminoketones with hydrazines, some dihydro-1,2,4-triazines were obtained. The possible 1,2-, 2,3-, or 5,6-dihydro structures were excluded by IR spectroscopic studies however, this method, as well as the attempted preparation of fixed derivatives, failed to distinguish between... 

There are five possible dihydropyrimidine forms, although most of the known dihydropyrimidines have either the 1,2- 491 or the tautomeric 1,4- 492 or 1,6-dihydro structures 493 <1986H(24)1433>. Of the three possible tetra-hydropyrimidine forms, the most commonly found is the 1,4,5,6-tetrahydro- or cyclic amidine structure 498. 

There are manifold possibilities for tautomerism in partially saturated derivatives. As an example, dihydro-1,2,4,5-tetrazines have been formulated in the 1,2-, 1,4-, 1,6- and 3,6-dihydro structures, but the 1,4-dihydro structure is probably the most stable (see also Section 3.2.2.3.2). 

There are five dihydropyrimidines (455)-(459). Most of those known have either the 1,2- or the tautomeric 1,4- or 1,6-dihydro structures. Gaussian 70 ab initio calculations of the energy of unsubstituted dihydropyrimidines yielded the following order of stability (457) > (456) > (455) > (458) > (459). The results agree with the experimentally observed behavior of these compounds... 

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