Pyrrolo pyrazines

Interesting constructs of molecules such as pyrrolo-pyridines, pyrrolo-quinolines, pyrrolo-pyrazines, pyrrolo-quinoxalines and pyrrolo-pyrimidines could be constructed by intramolecular Chichibain-type reaction. Davis and co-workers were the first to show the first of these examples, where p-methylazines react with nitriles to give the corresponding fused bicycle in the presence of excess base (2.5 equiv). For example, P-picoline reacts with benzonitrile in the presence of LDA to give the pyrrolo-pyridine adduct 61 in a 90% yield and traces of 62a. Under similar conditions and if... 

H,3H- Pyrrolo[l, 2-c]oxazole-l, 3-dione, 5,6,7,8-tetrahydro-IR spectra, 6, 978 [2.2](2,5)Pyrrolophane, N-aryl-rearrangements, 4, 209 Pyrrolophanes natural products, 7, 764 synthesis, 7, 771 Pyrrolophanes, N-aryl-synthesis, 7, 774 (2,4)Pyrrolophanes synthesis, 7, 771 Pyrrolo[3,4-c]pyran-4-ones synthesis, 4, 288 Pyrrolopyrans synthesis, 4, 525, 526 Pyrrolopyrazines synthesis, 4, 526 Pyrrolo[l, 2-a]pyrazines synthesis, 4, 516 Pyrrolo[2,3-6]pyrazines Mannich reaction, 4, 504 Vilsmeier reaction, 4, 505 Pyrrolo[3,4-c]pyrazole, 1,3a,6,6a-tetrahydro-structure, 6, 976 synthesis, 6, 1019 Pyrrolopyrazoles synthesis, 5, 164 Pyrrolo[l,2-6]pyrazoles synthesis, 6, 1002, 1006 Pyrrolo[3,4-c]pyrazoles reactions, 6, 1034 synthesis, 6, 989, 1043 Pyrrolo[3,4-c]pyrazolones synthesis, 6, 989 Pyrfolopyridazines synthesis, 4, 517 Pyrrolo[l, 2-6]pyridazines synthesis, 4, 297 6/7-Pyrrolo[2,3-d]pyridazines synthesis, 4, 291 2/f-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291 6/7-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291... 

Pyrrolo[l,2-fl]thieno[2,3-c]pyrazine (186) brominated mainly in the fused pyrrole ring. Only the third bromine atom introduced substituted the thiophene /3-position (86JHC17). 

One interesting example of this type of synthesis has been reported. 6-Phenyl-5//-5,7(6F/)-pyrrolo[3,4-/>]pyrazine (515) underwent electrolytic reduction in the presence of chlorotrimethylsilane to give the (unisolated ) substrate (516) that reacted with methyl acrylate (minimal detail) to afford a mixture of methyl 8-anilino-5-oxo-l,5-dihydro-6-quinoxalinecarboxylate (517) and methyl 5-ani-lino-8-oxo-4,8-dihydro-6-quinoxalinecarboxylate (517a) (17% and 21%, respectively, after separation). 

Besides furo[2,3-d]pyrimidines, 6-substituted 5H-pyrrolo[2,3-h]pyrazines have also been obtained in a microwave-promoted one-pot process starting from N-mesyl protected 2-amino-3-chloropyrazine (Scheme 60) [74]. The... 

Azomethine ylides of pyrrolo[l,2- ]pyrazine <1996JOC4655> and 3,4-dihydro pyrrolo[l,2-tf]pyrazine <1997T9341> undergo 1,3-dipolar cycloadditions with a number of dipolarophiles. For example, the ylide 178 reacts with propargylic ester 179 to give the tricyclic derivative 180 (Equation 43). 

The l,2,5-oxadiazolo[3,4-< ]pyrrolo[l,2- ]pyrazine derivative 185 was synthesized from the cr-chloroketone 184 and diaminooxazole 183. Some dihydro product 186 was also isolated (Equation 45) <1999CHE882>. 

Pyrazolo[4,3- ]pyrrolo[l,2- ]pyrazines were obtained by cyclodehydration of amide derivatives of pyrrolopyrazoles <2005M217>. 

Several bis-heterocyclopyridines have been previously demonstrated to have various central nervous system effects <1996CHEC-II(8)967>. Pyrrolo[l, 2- ]thieno[3,2-f ]pyrazines have been demonstrated to be high-affinity ligands for 5-HT3 receptors <1996JME2068>. Pyrazolo[4,3- ]pyrrolo[ l,2-tf]pyrazines have moderate antibacterial and antifungal activity <2005M217>. 

Pyrido[3, 2 4,5]pyrrolo[l,2- Pyrido[3, 4 4,5]pyrrolo[l,2-A]pyridazine <2005W02005013907>... 

Heating of 3,4-diamino-l,2,5-oxadiazole 156 and the relatively common 2-chloro-l,5-diketone gave 1,2,5-oxadi-azolo[3,4- ]pyrrolo[l,2- ]pyrazine 164 (Equation 27) <1999CHE882>. 

Upon reaction of A -vinyliminophosphoranes (109) with aromatic isocyanates, vinylcarbodiimides (110) are formed, as shown in Scheme 47. Divi-nylcarbodiimides (111) can be obtained as side products (88CB271). With isonitriles the vinylcarbodiimides also afford pyrroles (112) via [4 + 1]-cycloaddition. Divinylcarbodiimide can also react via [4 -l- l]-cycloaddition with an isonitrile, whereupon an electrocyclic step of the initial diaza-1,3,5-trienes (113) follows. Finally, the pyrrolo[2,3-e]pyrazine 114 is obtained (88CB271). 

Lunesta, (+)-(5iS )-6-(chlor/7ynVir -2-yl)-7-oxo-6.7-dihydro-5H-pyrrolo A-b pyrazin-5-y 1-carboxylate... 

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