- On Pyridopyrazinol Chemistry: Synthesis of Chemiluminescent Substances
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Our work on new chemiluminescent substances related to the marine luciferin coelenterazine (λ max= 465 nm) led us to attempt the synthesis of four nitrogen-rich pyridopyrazine-bearing analogues. Accordingly, the preparation of the corresponding benzyl-bearing pyridopyrazinols is studied. By varying the conditions for the condensation of phenylpyruvic acid with 1,2-diaminopyridine or 3,4-diaminopyridine, all the possible pyridopyrazin-2-ol regioisomers are isolated and properly characterized, including by means of crystallographic studies. The ensuing syntheses of the halogenated pyridopyrazines are fraught with difficulties ranging from extensive decomposition to an unexpected ring contraction. In one instance, the inherently reductive mixture of phosphorus oxychloride and phosphorus trichloride provides 2-benzyl-3-chloropyrido[2,3- b ]pyrazine. This precursor is then transformed into the target O -acetylated luciferin (6,8-dibenzylimidazo[1,2- a ]pyrido[3,2- e ]pyrazin-9-yl acetate). The 'benzo' derivative of this analogue (i.e., 2,12-dibenzylimidazo[1′,2′:1,6]pyrazino[2,3- c ]isoquinolin-3-yl acetate) is also prepared and the chemiluminescence emission spectra of these compounds are determined in a phosphate buffer (λ max= 546 and 462 nm).
- Gagnot, Glwadys,Legrand, Pierre,Tadros, Amira,Ezzahra Hibti, Fatima,Quatela, Alessia,Janin, Yves L.
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- Palladium-catalyzed enolate arylation as a key C-C bond-forming reaction for the synthesis of isoquinolines
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The palladium-catalyzed coupling of an enolate with an ortho-functionalized aryl halide (an α-arylation) furnishes a protected 1,5-dicarbonyl moiety that can be cyclized to an isoquinoline with a source of ammonia. This fully regioselective synthetic route tolerates a wide range of substituents, including those that give rise to the traditionally difficult to access electron-deficient isoquinoline skeletons. These two synthetic operations can be combined to give a three-component, one-pot isoquinoline synthesis. Alternatively, cyclization of the intermediates with hydroxylamine hydrochloride engenders direct access to isoquinoline N-oxides; and cyclization with methylamine, gives isoquinolinium salts. Significant diversity is available in the substituents at the C4 position in four-component, one-pot couplings, by either trapping the in situ intermediate after α-arylation with carbon or heteroatom-based electrophiles, or by performing an α,α-heterodiarylation to install aryl groups at this position. The α-arylation of nitrile and ester enolates gives access to 3-amino and 3-hydroxyisoquinolines and the α-arylation of tert-butyl cyanoacetate followed by electrophile trapping, decarboxylation and cyclization, C4-functionalized 3-aminoisoquinolines. An oxime directing group can be used to direct a C-H functionalization/bromination, which allows monofunctionalized rather than difunctionalized aryl precursors to be brought through this synthetic route.
- Pilgrim, Ben S.,Gatland, Alice E.,Esteves, Carlos H. A.,McTernan, Charlie T.,Jones, Geraint R.,Tatton, Matthew R.,Procopiou, Panayiotis A.,Donohoe, Timothy J.
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p. 1065 - 1090
(2016/01/15)
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- New fluorescent isoquinoline derivatives
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Various structural modifications of 3-amino and 3-hydroxyisoquinolines have been carried out to provide new fluorescent derivatives. The transformations involved nucleophilic substitution of a bromine atom or a triflate moiety at positions 1 and 3, respectively, as well as the condensation reaction of a 3-amino group with triethyl orthoformate and subsequent transformation with amines to give amidines. The new compounds have been studied by fluorescence spectroscopy.
- Balog, József,Riedl, Zsuzsanna,Hajós, Gy?rgy,Miskolczy, Zsombor,Biczók, László
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p. 5264 - 5266
(2011/10/19)
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- Interconversion of nitrenes, azirenes, and diradicals: Rearrangement of 3-isoquinolylnitrene to o-cyanophenylketenimine and 1-cyanoisoindole
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Photolysis of tetrazolo[1,5-b]isoquinoline/3-azidoisoquinoline 22T/22A generates 3-isoquinolylnitrene 23, which has been characterized together with a diradical species (25) by Ar matrix ESR spectroscopy. Photolysis at λ > 300 nm generates azirene 24, characterized by IR spectroscopy, whereas further broadband UV photolysis destroys the azirene to produce o-cyanophenylketenimine 17. The use of 15N-labeled tetrazole/azide 22T′/22A′ demonstrates rapid equilibration of two regioisomeric 15N-labeled azirenes 24′ and 24″ prior to formation of 17. Flash vacuum thermolysis (FVT) of 22T/22A affords 1-cyano-2H-isoindole 27 in quantitative yield. FVT of 15N-labeled tetrazole/azide 22T′/22A′ causes scrambling of 15N label in the 1-cyano-2H-isoindole product. It is concluded that the interconversion of azirenes 24 takes place via the unobserved diazacycloheptatetraene/ diazacycloheptatrienylidene 32/33, and that the rearrangement of azirene to ketenimine 17 and 1-cyanoisoindole 27 takes place via reversion to nitrene 23 followed by ring opening to diradical 25.
- Vosswinkel, Michael,Lueerssen, Holger,Kvaskoff, David,Wentrup, Curt
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p. 1171 - 1178
(2009/07/25)
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- A general approach to 3-aminoisoquinoline, its N-mono and N,N-disubstituted derivatives
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Condensation of 2-cyanomethyl benzaldehydes 1 with 2 (ammonia, primary or secondary amines) carried out in the presence of a catalytic amount of trifluoroacetic acid, afforded 3-aminoisoquinolines 3. In the case of primary amines azomethines 4 were formed at first; they dissociated and subsequently yielded 3 in a rather slow process.
- Zdrojewski,Jonczyk
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p. 12439 - 12444
(2007/10/02)
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