Pyrido pyrimido pyridines

The ring fused onto the parent has the suffix o common names are used (with modification) where possible to simplify the name. Some examples are pyrido for pyridine, pyrrolo for pyrrole, thieno for thiophene, furo for furan, imidazo for imidazole, pyrimido for pyrimidine, pyrazino for pyrazine, among others. 

Pyrido- and pyrimido[l, 4]diazepinones have been produced by condensing pyridinediamines and a pyrimidinediamine with esters of /i-oxo acids. Because of the unsymmetrical structures of the diamines the reactions may take two courses, as exemplified by the action of ethyl acetoacetate on pyridine-2,3-diamine.308... 

Reaction of pyridines with dialkyl acetylenedicarboxylates in the presence of isocyanates in dry CH2C12 at room temperature produced 1-substituted 2-oxo-l,9a-dihydro-2/7-pyrido[l,2-tf]pyrimidine-3,4-dicarboxylates <2004TL1803>. One-pot, three-component synthesis of 1-substituted 2-oxo-l,llb-dihydro-2//-pyrimido[2,l- ]iso-quinoline-3,4-dicarboxylates and 4-(3-chloro-4-methylphenyl)-3-oxo-4,4a-dihydro-3/7-pyrimido[l,2-tf]quinoline-l,2-dicarboxylate was realized by the reaction of isoquinoline and quinoline with isocyanates and dialkyl acetylenedicarboxylates <2004S861>. Diastereomeric mixtures of l-tosyl-2-aryl-l,llb-dihydro-2/7-pyrimido[2,Ttf]isoquinoline-3,4-dicarboxylates were obtained from isoquinoline, iV-tosyl-benzaldehyde imines, and DMAD <2002OL3575>. 

The pyrimidothiazine (204) extrudes sulfur at 130 °C to give the pyrrolopyrimidine (205 Scheme 64) (71TL4185). (-Butoxybis(dimethylamino)methane (BBDM) is a substitute for dimethylformamide dimethyl acetal. It is used to prepare the pyrimido[5,4-c]pyridazine (206). Hydrogenation gives the pyrrolopyrimidine (207 78% Scheme 65) (78JOC2536). By a similar reduction, pyrido[3,2-c]pyridazine is converted into pyrrolo[3,2-6]pyridine (80RCR428). 

Aminouracil is cyclized by JV,A-dimethylphosgeneiminium chloride and pyridine to give the tricyclic pyrido[r,2 l,2]pyrimido[4,5-fif pyrim-idine-2,4-dione (81TL449 83JHC575) (Scheme 126). 

Selective bromination at C-5 of A -substituted uracils has been achieved by using CHBrj-Oj [93ACS(47)1117]. A novel three-component reaction of (uracil-6-ylimino)phosphorane, isocyanate, and pyridines has been used to prepare pyrido[r,2 3,4]pyrimido(4,5-d]pyrimidines (76). In a similar way, pyri-mido[4, S 4,S pyrimido[6,l-a isoquinoline and -phthalazine (77) have been constructed 193JOC(58)6976],... 

The novel three-component reaction of (utacil-6-ylimino)phosphorane (34), isocyanate and substituted pyridines, yields the new pyrido[T,2 3,4]pyrimido[4,S-d]pyridines (35). The use of isoquinoline or phthalazine yields (36 X= CH, or N). 

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