Derivation of fluorine-containing pyridine dicarboxylates IV. N-substituted dihydropyridine derivatives

The bio-activity observed for certain Hantzsch derived fluorine-containing dihydropyridinecarboxylates 6, 11 and 12 and pyridinecarboxylates 10 prompted the preparation of a number of related N-substituted dihydropyridines for the first time. One method involved a mixed Hantzsch sequence to give 2 from which unexpected side products 3–5 were also isolated and identified. A second preparative method relied on lithiobase deprotonation of 6, 11 and 12 followed by alkylation or acylation to give products 7–9 and 13–15 . Structure determination and stereo-assignments are discussed in terms of their spectral properties, and reaction mode.     

Derivation of fluorine-containing pyridinedicarboxylates. III Regio-selective anion chemistry at the 2- and 4-position

In contrast of Part II of the series, 4-alkyl-2-(difluoromethyl)-6-(trifluoromethyl)-3,5-pyridinedicarboxylates, 1 , were reacted with various strength bases to effect regio-selective reaction of electrophiles at either the benzylic carbanion of the 4-position, or at the 2-(difluoromethyl)carbanion. Weaker bases up to and including potassium butoxide or lithium bis(trimethylsilylamide) effected reaction of 1 at the 4-position to produce 2 and 3 by Stobbe-type condensations of aldehydes and ketones. In similar manner carbon disulfide, carbon dioxide, alkyl halides, silyl halides, and hexachloroethane produced the highly functionalized derivatives 4-10. In contrast, use of lithium diisopropylamide and like bases selectively effected carbanion formation at the 2-position to form, with the cited electrophiles and others, substitution products 11. The latter were further derived to the highly functional materials, 12-19.     

Ir-catalyzed direct borylation at the 4-position of pyrene

The first direct borylation of a C-H bond at the 4-position of pyrene was achieved using [Ir(COD)Cl](2)/dtbpy as the catalyst precursor and B(2)pin(2) as the boron source. The position-related photophysical properties of pyrene derivatives are reported.     

Regiospecific introduction of alkyl groups into 4-position of pyridine novel synthesis of 4-substituted pyridines

Regiospecific synthesis of 4-substituted pyridines is attained $\text{via}$ alkylation of diisopropyl 1-ethoxycarbonyl-1, 4-dihydropyridine-4-phosphonate followed by treatment with butyllithium. The phosphonate is prepared directly from pyridine in one pot.     

Selective esterification of the polyphenol resveratrol at the 4′-position

Selective esterification of the polyphenol resveratrol was performed under thermodynamic conditions using NaH and acid anhydrides to directly access 4′-esters. Standard conditions with acetyl chloride and pyridine showed poor selectivity, favoring esterification at the 3-position. The extended 4′-phenolate anion is generated in preference to the 3-phenolate under the new anhydride-sodium hydride-DMSO conditions. Acylation occurs to access the 4′-ester products with modest selectivity and yield with minimal formation of the 3-monoester, 3,5-diester, and triester products.     

The microanalysis of fluorine-containing organic compounds. II. the determination of fluorine

Summary The compound is decomposed by fusion with metallic sodium or potassium in a nickel bomb of special design, and the fluorine is titrated with thorium nitrate solution. Several modifications of this titration procedure were first examined as a means of completing the determination, but only one was found suitable, i. e. back-titration of a comparison solution with a standard sodium fluoride solution.When nitrogen and sulphur, which form cyanide and sulphide ions, are present, the procedure has to be modified slightly to overcome their interference.

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Zusammenfassung Organische Fluorverbindungen werden durch Schmelzen mit metallischem Natrium bzw. Kalium in einer Nickelbombe besonderer Konstruktion zerstört und das Fluor mit Thoriumnitratlösung titriert. Einige Modifikationen dieses Titrationsverfahrens wurden zunächst geprüft, aber nur eine davon erwies sich endgültig als für die Bestimmung geeignet: die Rüektitration einer Vergleichalösung mit einer Standardlösung von Natriumfluorid.Bei Gegenwart von Stickstoff und Schwefel bilden sich Cyanidbzw. Sulfidionen, deren störender Einfluß durch eine kleine Abänderung des Verfahrens ausgeschaltet werden muß.

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Résumé Les composés organiques fluorés sont décomposés par fusion avec le sodium métallique ou le potassium dans une bombe de nickel de construction spéciale et le fluor est titré avec le nitrate de thorium en solution. Plusieurs modifications de ce mode de titrage furent d'abord examinées pour terminer le dosage, mais un seul fut trouvé convenable, le titrage par retour d'une solution de comparaison avec une solution de fluorure de sodium.Quand l'azote et le soufre qui forment des ions cyanhydriques et suifhydriques sont présents, le procédé doit être légèrement modifié afin d'empêcher leur interférence.

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The paper byR. Belcher andR. Goulden, Mikrochem.37, 679 (1951) is considered as Part I of this series.     

Chemistry of thienopyridines. XXX. Elaboration of the substituent in 6-cyanothieno[2,3-b]pyridine

Ten derivatives of thieno[2,3-b]pyridine bearing substituents at the 6-position are obtained from transformations which start with 6-cyanothieno[2,3-b]pyridine (2). Treatment of 2 with sodium alkoxide-alkanol gives imidates (3) in ca. 85% yield. Methyl imidate 3a reacts, in turn, with ammonium chloride to produce a carboxamidine (84%), with 1,ω-alkyldiamines to form cyclic amidines, and with Meldrum's acid to give an aminoester intermediate (4) (36%). Various reagents then convert 4 into the acetyl derivative (86%) (also obtained directly from 2), an unsaturated aminoester (6) (80%), and a β-ketoester (7) (39%). Spectral data are reported for these compounds.     

Intramolecular nucleophilic cyclization of 3-substituted pyridylalkylamines onto the 2-position of the pyridine ring

The intramolecular nucleophilic cyclization of 4-(3-pyridyl)butylamine ( 4a ) to yield 6,7,8,9-tetrahydro-5H-pyrido[2,3-b]azepine ( 5 ) was investigated. Of eleven different alkali metal reagents sodium, sodium hydride, sodium amide, and potassium hydride gave good yields of 5 . The sodium conditions when applied to 3-(3-pyridyl)propylamine ( 4b ) afforded 1,2,3,4-tetrahydro-1,8-naphthyridine ( 6 ) in good yield.     

Oxygenation of 2,6-di- -butylphenols bearing electron-withdrawing group at 4-position mediated by Co(II)-schiff base complex

4-Acyl-2,6-di- -butylphenols except 3,5-di- -butyl-4-hydroxybenzaldehyde were oxygenated in the presence of Co(Salpr) exclusively at the ortho position to give the corresponding 3,5-di- -butyl-6-hydroperoxy-2,4-cyclohexadienone derivatives in quantitative yield.     

Dipole stabilized α-amino carbanions. II. Alkylation of tetrahydroisoquinolines in the 1-position.

N-Formamidine derivatives of tetrahydroisoquinolines are metalated and alkylated to give 1-substituted derivatives. Regeneration of the parent amine is accomplished by several different reagents.