Pyridines 2-alkoxy

Recently, research into new organometallic compounds has accelerated. Group 4 metal alkyl complexes incorporating 8-quinolino ligands [58] and bidentate pyridine-alkoxy ligands [59] are reported by Jordan. Moreover, it was reported that a very simplified catalyst, Ni(II)(dppe) or Pd(II)(dppp), produced hyperbranched PF by Sen [60]. 

Oxa2oles react with dienophiles to give pyridines after dehydration or other aromatization reactions (69,70). A commercially important example is the reaction of a 5-aLkoxy-4-methyloxa2ole with 1,4-butenediol to yield pyridoxine (55), which is vitamin... 

DL-Alk-2-enopyranos-4-uIose, 2,3-dideoxy-synthesis, 1, 426 Alkoxy nitroxide radicals pyridines ESR, 2, 146 Alkyl cyanides trimerization, 3, 503 Alkylating agents as pharmaceuticals, 1, 157 Alkylation... 

A different set of tautomeric tetrahydropyridines was obtained on partial hydrogenation of 2-alkoxy-3-acylpyridines 25 on PtOa or Pd/C catalyst (Scheme 9) (79JHC939). The tetrahydropyridines 26 formed exist exclusively as single tautomers, the type of tautomer, however, being determined by the substitution in the pyridine ring. 

Hoomaert has studied Diels-Alder reactions of pyridine oquinodimethane analogs generated from functionalized o-bis(chloromethyl)pyridines <96T(52)11889>. The photochemical cycloaddition of 2-alkoxy-3-cyano-4,6-dimethylpyridine with methacrylonitrile gives a bicyclic azetine, 6-alkoxy-3,5-dicyano-2,5,8-trimethyl-7-azabicyclo[4.2.0]octa-2,7-diene, in moderate yield <96CC1349>. Regiospecific hydroxylation of 3-(methylaminomethyl)pyridine to 5-(methylaminomethyl)-2-(17/)-pyridone by Arthrobacter ureafaciens has been reported <96MI173>. 

Photochemical [2+2]cycloaddition between benzo[b]furan and 3-cyano-2-alkoxy-pyridines in benzene has been reported to follow a very interesting mechanism supported also by Frontier-MO calculations using the PM3 Hamiltonian. It is believed that the singlet excited state of the pyridine and the ground state benzofuran react to form a [2+2] adduct and is followed by ring opening to the cyclooctatriene, which cyclizes to the secondary endo- and exo-isomers shown below <00CC1201>. 

Treatment of a-hydroxy- or a-alkoxy-substituted hexahydro-oxazolo[3,4-r ]pyridin-3-ones with an acid allows for the generation of bicyclic iV-acyliminium ions which can then smoothly react with nucleophiles, usually with high diastereoselectivities (Scheme S3) <2001EJ01267, 1998SL206>. 

As demonstrated in previous sections, the carbazole unit was introduced as a pendant group or as a chain member in major classes of EL polymers such as PPVs (95-105,141,177, 190) and PFs (62, 63, 242-245). A variety of 2,7-carbazole-derived polymers with different conjugated units, such as 2-alkoxy- and 2,5-dialkoxy-l,4-phenylene (549) and l,l -binaphtha-lene-6,6 -diyl (550 [658]), 2,5-pyridine (551), 2,7-fluorene (245 [345,346]), 2,5 -bithiophene (554 [345]), 5,8-quinoxaline (552), quinquethiophene-SjS -dioxide (450 [550]), 2,5-thiophene (553), 2,5-furan (555), and acetylene (556 [659]) were reported by Leclerc and coworkers... 

Inverse type hetero-Diels-Alder reactions between p-acyloxy-a-phenylthio substituted a, p-unsaturated cabonyl compounds as 1-oxa-1,3-dienes, enol ethers, a-alkoxy acrylates, and styrenes, respectively, as hetero-dienophiles result in an efficient one step synthesis of highly functionalized 3,4-dihydro-2H-pyrans (hex-4-enopyranosides). These compounds are diastereospecifically transformed into deoxy and amino-deoxy sugars such as the antibiotic ramulosin, in pyridines having a variety of electron donating substituents, in the important 3-deoxy-2-gly-culosonates, in precursors for macrolide synthesis, and in C.-aryl-glucopyranosides. 

Other chemical reagents that have been used to dehydrogenate are diphenyl disulfide for 1,2,3,4-tetrahydrocarbazole itself, N-bromosuccinimide in pyridine for 1-ethoxycarbonyl-1,2,3,4-tetrahydrocarbazole, selenium dioxide for 9-methyl-1,2,3,4-tetrahydrocarbazole (a 1 5 mixture of 9-methyl-carbazole and 1-oxo-1,2,3,4-tetrahydrocarbazole was obtained ), and manganese dioxide to aromatize 1-methyl- and l,4-dimethyl-6-alkoxy-3-formyl-1,2,3,4-tetrahydrocarbazoles and 1,9-diprenyl-1,4-dihydrocarba-zole. ... 

Many analogs of 75 with substituents in the pyridine rings have also been prepared ° although 6-alkoxy-2,2 -bipyridines react with ethylene dibromide to afford the pyridone 76 rather than 4-alkoxy analogs of 75. Derivatives of 75 with alkyl substituents on the ethylene bridge (i.e., 6 and/or 7 positions) can likewise be prepared from 2,2 -bipyridines and appropriate dibromoalkanes. " " 6-Hydroxy-substituted derivatives of 75, for example, compound 78, are accessible by ring closure of j8-carbonyl monoquaternary salts of 2,2 -bipyridine, such as compound 77, with acid. 

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