Pyridyl Alcohols Research Articles

ChemInform Abstract: Catalyzed Asymmetric Reaction of Aldehydes with Dialkylzinc in the Presence of Chiral Pyridyl Alcohols as Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalysed asymmetric reaction of aldehydes with dialkylzinc in the presence of chiral pyridyl alcohols as ligands

The synthesis of homochiral pyridyl alcohols ( 1,2,3a-c) and a catalytic asymmetric addition of dialkylzinc to various aldehydes using 1-3 as ligands are described. Although the reaction of benzaldehyde with Et 2Zn in the presence of (S)- 1 and (R,R)- 2 gave (S)- and (R)-1-phenyl-1-propanol, respectively, in moderate enantiomeric excess (e.e.), tridentate ligands ( 3a-c) accelerated the reaction to produce the corresponding alcohols in high e.e. Particularly, (S)- 3b was found to be the most efficient catalyst, for which asymmetric reactions of various aldehydes with dialkylzinc gave the corresponding alcohols in good to high e.es. (up to 95% e.e.).

ChemInform Abstract: Through‐Bond Modulation of N → B Ring Formation Shown by NMR and X‐Ray Diffraction Studies of Borate Derivatives of Pyridyl Alcohols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Through-bond modulation of N→B ring formation shown by NMR and X-ray diffraction studies of borate derivatives of pyridyl alcohols

The preparation of diphenyl(2-pyridylmethoxy-O,N)borane (2a), diphenyl[1-(2-pyridyl)ethoxy-O,N]borane (2b), diphenyl[α-(2-pyridylbenzyloxy-O,N)]borane (2c), diphenyl[2-(2-pyridyl)ethoxy-O,N]borane (4), benzene-1,2-diyldioxy(2-pyridylmethoxy-O,N)borane (5) and benzene-1,2-diyldioxy[2-(2-pyridyl)ethoxy-O,N]borane (6) is reported. The cyclic structures 2a and 4 were established by X-ray diffraction studies, the N→B bond distance being 1.642 Å for 2a and 1.685 Å for 4. Complete assignment of the 1H and 13C NMR spectra of 2a–c and 4 was achieved from two dimensional HETCOR data. Additional evidence for the strength of the five- and six-membered rings in boron esters was obtained from variable-temperature measurements which show partial ring opening for the six-membered ring compounds at 180 °C. The observation that five-membered rings are more stable than six-membered ones is attributed to sigma-assistance by through-bond interactions.

ChemInform Abstract: Design and Synthesis of the Chiral Ligands for the Highly Enantioselective Asymmetric Reactions of Carbonyl Compounds

Several chiral ligands were designed and synthesized which perform highly enantioselective asymmetric reactions of carbonyl compounds. Enantioselective reduction of ketones with lithium borohydride modified with N, N'-dibenzoylcystine (or N-benzoylcystein) and tent-butyl alcohol (or ethanol) provided optically active sec.-alcohols in up to 9293% e.e. Functionalized ketones such as α-, β- haloketones, α- and β-aminoketones, pyridyl ketones, and fl-ketoesters were also reduced enantioselectively to afford opticall active epoxides, oxetanes, aminoalcohols, pyridyl alcohols, and β-hydroxyesters in high e.e.'s. Chiral pyrrolidinylmethanols, N, N-dibutylnorephedrine (DBNE), chiral piperazine, and polymer bound N-alkylnorephedrine were efficient chiral catalysts of the enantioselective addition of dialkyl zincs to aldehydes. Alkylation of both aliphatic and aryl aldehydes afforded optically active sec-alcohols in high e.e.'s. Formylesters afforded optically active lactones. Enantioselective conjugate addition of dialkyl zincs to enones was catalyzed by chiral complex prepared from DBNE and Ni (acac) 2 or NiBr2.

カルボニル化合物の高エナンチオ選択的不斉反応を目的とする不斉配位子の設計と合成

Several chiral ligands were designed and synthesized which perform highly enantioselective asymmetric reactions of carbonyl compounds. Enantioselective reduction of ketones with lithium borohydride modified with N, N'-dibenzoylcystine (or N-benzoylcystein) and tent-butyl alcohol (or ethanol) provided optically active sec.-alcohols in up to 9293% e.e. Functionalized ketones such as α-, β- haloketones, α- and β-aminoketones, pyridyl ketones, and fl-ketoesters were also reduced enantioselectively to afford opticall active epoxides, oxetanes, aminoalcohols, pyridyl alcohols, and β-hydroxyesters in high e.e.'s. Chiral pyrrolidinylmethanols, N, N-dibutylnorephedrine (DBNE), chiral piperazine, and polymer bound N-alkylnorephedrine were efficient chiral catalysts of the enantioselective addition of dialkyl zincs to aldehydes. Alkylation of both aliphatic and aryl aldehydes afforded optically active sec-alcohols in high e.e.'s. Formylesters afforded optically active lactones. Enantioselective conjugate addition of dialkyl zincs to enones was catalyzed by chiral complex prepared from DBNE and Ni (acac) 2 or NiBr2.

Nuclear magnetic resonance chemical shifts for alcoholic and phenolic protons in dimethyl sulphoxide: utility as a structural parameter

The n.m.r. spectra of various pyridyl alcohols and phenols were measured in dimethyl or [2H6]dimethyl sulphoxide. Pyridyl alcohols were classified into three categories on the basis of their n.m.r. behaviour. In cases in which the hydroxy-proton was sufficiently fixed in space through intermolecular hydrogen bonding with the solvent, the n.m.r. signal was a triplet due to coupling with the α-methylene group. The δOH value was found to be temperature dependent and to vary with change of the structural nature of hydroxy-group. Various types of intra- and intermolecular hydrogen bonding interactions are invoked for the elucidation of n.m.r. patterns. Several N-methylated pyridyl alcohols were subjected to n.m.r. investigation, but failed to provide well resolved n.m.r. patterns. The correlation between δOH and pKHA of the corresponding phosphates proved the reliability of δOH as a structural parameter for a linear free energy relationship study of phosphate hydrolysis.