7.9- Dihydro-6//-pyrido

The synthesis of 7,9-dihydro-6//-pyrido[2,l-rf][l,5]benzothiazepines (115) was carried out by reaction of 93 with acetone or 2-butanone in the presence of p-toluenesulfonic acid. The reaction also afforded compounds 116 and 117, which were detected by GC/MS analysis and not isolated (Scheme 35) (89LA601). 

Diphenyl-(pyrido-[3,4-b]-pyrazin) kann in alkalischem Methanol mit hoher Aus-beute in das 2,3-Diphenyl-3,4-dihydro- pyrido- 3,4-b)-pyrazin) (90% d.Th. F 247°) iiberfiihrt werden2 ... 

Zur reduzierenden Acetylierung von 3-Phenyl-bzw. 2,3-Diphenyl- pyrido-[2,3-b]-py-razin) in Acetonitril/Acetanhydrid zu 2-Phenyl-1,4-diacetyl-1,4-dihydro- (25% d.Th.) bzw. 2,3-Diphenyl-5-acetyl-5,8-dihydro-(pyrido[2,3-b]-pyrazin) (91% d.Th.) s. Lit.2 ... 

When pyridinium A -imine salts 157 were reacted with methylphenyl-cyclopropenone (158, R = Ph, R = Me) in the presence of a base, dihydro-pyrido[l,2-h]pyridazin-3-ones (159) were formed, which subsequently underwent oxidation to produce 3//-pyrido[l,2-h]pyridazin-3-ones (160) under the reaction conditions [76JCS(CC)275 78JOC2892], In some cases the dihydro intermediates (159) could be isolated. 3-Substituted derivatives (157, R = 3-Me, 3-CN R = H) gave mixtures of isomers of 160 (R = 5-... 

Bei dieser Reaktion konnen allerdings auch Kohlensaure-bis-hydrazide entstehen. So cyclisiert l-Amino-2-oxo-4,6-diphenyl-l,2-dihydro-pyridin mit Kohlensaure-bis-imidazolid zu 5,7-Di-phenyl-(pyridio[2,l-b]-l,3,4-oxadiazolium )-2-olat innvA 37%iger AusbeutelS0(vgl. S. 533, 535). AuBerdem wird 1,3-Bis-[4,6-diphenyl-2-oxo-l, 2-dihydro-pyrido -harnstoff (45%) gebildet. 

Pyrido[3,4-c]furazane (z. B. II) lassen sich mit Natriumboranat reduzieren wahrend bei 20° zu 65% 6-Cyan-4,7-diphenyl-4,5-dihydro- pyrido[3,4-c]furazan) entsteht, erhalt man beim Ko-chen unter RiickfluB zu 79% 6-Cyan-3,4-diamino-2,5-diphenyl-pyridinn3 ... 

Quiroga, J., Cisnero, C., Insuasty, B., Abonia, R., Nogueras, M. and Sanchez, A., A regiospecific three-component one-step cyclocondensation to 6-cyano-5, 8-dihydro pyrido [2,3-d]pyrimidin-4-(3H) ones using microwaves and solvent-free conditions, Tetrahedron Lett., 2001, 42, 5625-5627. 

More recently, an approach based on bromides 62 was employed in the synthesis of other dipyridothiophenes (1996KGS553, 1997T13351). In particular, 6,9-dihydro-pyrido[3,2, 4,5]thieno[3,2-6]pyridines 64 were prepared for the first time from thiolates 65. It should be emphasized that cascade heterocyclization occurs spontaneously in the absence of a basic catalyst (1996KGS553). 

The starting material is produced by reacting 6-amino-2-methylthiopyrimidine with ethoxymethylene malonic acid diethyl ester. That intermediate is thermally treated in diphenyl ether to give 6-ethoxycarbonyl-2-methylthio-5-oxo-5,8-dihydro-pyrido[2,3-d]pyrimidine. The ethoxy group is hydrolyzed off with sodium hydroxide and one nitrogen is ethylated with diethyl sulfate to give the starting material. These are the same initial steps as used in the pipemidic acid syntheses earlier in this volume. 

Benzoylhydrazinopyridine (239b) was refluxed in methanolic HC1 to give the dihydro pyrido-... 

Benztriazole6,7 und verwanute Verbindungen (z.B. Naphtho-[2,3-d]-triazoln, Pyri-do-[2,3-d]-triazole8, die mesoionischen 3-Oxo-2,3-dihydro-(pyrido-[2,l-c]-l,2,4-tri-azole)9 und Pyrido-tetrazole12 werden, zumeist mit Palladium-Katalysatoren, partiell und selektiv im annellierten Ring (unter Erhalt eines in der 2-Position substituierten Benzol-Kerns hydriert. 

A series of ethyl 2-R(Ar)-9-cyclopropyl-4-fluoro-6-oxo-lH-imidazo[4,5-/i] quinoline-7-carboxylates 78 have been obtained through cyclocondensations of the corresponding 7,8-diamino qninolones [233], Also a number of tetracyclic [h]-annelated fluoroquinolones, snch as l-cyclopropyl-6-fluoro-4-oxo-l,4-dihydro-pyrido[2,3-fl]carbazole-3-carboxylic acids 79 and their thiene isosters have been obtained (Scheme 36) [198], All derivatives proved to possess a high activity against Bacillus subtilus and Staphylococci. 

The corresponding saturated dialkylamino ketones (Mannich bases) have also been used to provide 5,6-dihydro derivatives, which are oxidized in air to aromatic pyrido[2,3-[Pg.229]

The NMR spectra of the parent compounds of the pyrido-[2,3-d]- and -[3,4- f]-pyridazine systems have been studied, together with those of some closely related derivatives parent compound, 282). In the pyrido[4,3-c]pyridazine series, only the spectrum of the dihydro compound (302) has been recorded <79X2027). 

The 6- and 7-quaternary salts of pyrido[2,3-d]pyridazine are reduced by borohydride with subsequent air oxidation to 5,6- and 7,8-dihydro oxo derivatives respectively (77BSF919), whilst the [3,4-d] analogues give the corresponding 1,2- and 3,4-dihydro oxo compounds 72CR(C)(275)1383). ... 

H,4H-Oxazolo[5,4,3-y]pyrido[3,2-g]quinolin-4-one, 8-hydroxymethyl-6-methyl — see Nybomyein 5H-Oxazolo[2,3-[Pg.731]

Pyrido[3,4-d]pyridazine, 1,4-dimorpholino-biological activity, 3, 261 Pyrido[4,3-c]pyridazine, dihydro-NMR, 3, 234 UV spectra, 3, 236... 

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