Adjacent Hydroxy Groups Research Articles

Isomeric Benzenediol-Linked Organophosphonates as a Handy Reusable Emitting Platform: Diversity in Polyamine Vapor Detection.

This work introduces metal/column-free facile quantitative access to conformationally twisted catechol-linked organophosphonate (CAP) as a blue-emitting solid that could reversibly detect only 1,3-diaminopropane (DAP) and 1,2-ethylenediamine (EDA) vapors, belonging to industrially and pharmaceutically abundant crucial diamines. In CAP, two adjacent hydroxy groups in a benzene ring facilitate selective diamine-dihydroxy (amine-phenol type) interactions in the solid phase, leading to a quenched emission with selectively smaller aliphatic PAs, that is, DAP and EDA. The disparity was noticed with an isomeric resorcinol-linked emitter (RAP), detecting various polyamine vapors with superior sensitivity. A one-carbon-away placed hydroxy group in RAP can only generate a monoamine-hydroxy complex, not diamine-dihydroxy. The more acidic nature of resorcinol would prefer ionizing the amines and, consequently, creating amine/hydroxy interactions. More systematic investigations reveal an exciting role of amine-hydroxy realization for the catechol analog in the solid phase with a syn-anti conformation for CAP. Unlike CAP, RAP's available crystal void space creates considerable room in which to come closer and facilitates amine-phenol interactions. The role of phosphonates in the selective detection of PAs is also examined. Observed outcomes are substantiated by FT-IR, single-crystal X-ray diffraction, SEM, XPS, and mass spectroscopic studies. The proposed amine-hydroxy interactions are further supported by DFT-optimized molecular structures.

Studies on the mechanochemically induced chromene-annulation of meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin: Non-innocence of the grinding aids

The modification of chlorins to fine-tune their optical properties is important for their application in medical and technical fields. The solution phase, base-induced formation of a chromene-annulated chlorin from the corresponding meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin by intramolecular S[Formula: see text]Ar displacement of an [Formula: see text]-F atom of a meso-aryl group by an adjacent hydroxy group is well-known. Organic transformations performed by grinding the dry reagents together promise to be a much greener and possibly simpler method compared to traditional solution-based reactions. However, the use of such mechanochemical approaches to accomplish porphyrinoid chromophore modifications are virtually unexplored. We report here the translation of the solution-based base-induced formation of a chromene-annulated chlorin to a solid state mechanochemical reaction in a planetary powder mill. The factors determining the success (and failure) of the reaction are delineated. While this report shows that porphyrinoid framework modifications can principally be induced mechanochemically, the mechanochemical reaction is not (yet) competitive with the solution state reaction. The outcome of the reaction is very sensitive to the particular milling conditions, specifically-and importantly as it is unexpected – the grinding aids used. What we previously believed to be inert or merely basic aids affected a significant degradation of the chlorins under the milling conditions, a finding that might generally limit mechanochemical approaches in porphyrinoid chemistry, or at least require careful adjustments.

Intramolecular H-Bond Dynamics of Catechol Investigated by THz High-Resolution Spectroscopy of Its Low-Frequency Modes.

Catechol is an oxygenated aromatic volatile organic compound and a biogenic precursor of secondary organic aerosols. Monitoring this compound in the gas phase is desirable due to its appreciable reactivity with tropospheric ozone. From a molecular point of view, this molecule is attractive since the two adjacent hydroxy groups can interchangeably act as donor and acceptor in an intramolecular hydrogen bonding due to the tunnelling between two symmetrically equivalent structures. Using synchrotron radiation, we recorded a rotationally-resolved Fourier Transform far-infrared (IR) spectrum of the torsional modes of the free and bonded -OH groups forming the intramolecular hydrogen bond. Additionally, the room temperature, pure rotational spectrum was measured in the 70–220 frequency range using a millimeter-wave spectrometer. The assignment of these molecular transitions was assisted by anharmonic high-level quantum-chemical calculations. In particular, pure rotational lines belonging to the ground and the four lowest energy, vibrationally excited states were assigned. Splitting due to the tunnelling was resolved for the free -OH torsional state. A global fit combining the far-IR and millimeter-wave data provided the spectroscopic parameters of the low-energy far-IR modes, in particular those characterizing the intramolecular hydrogen bond dynamics.

One-Pot γ-Lactonization of Homopropargyl Alcohols via Intramolecular Ketene Trapping.

A one-pot γ-lactonization of homopropargyl alcohols via an alkyne deprotonation/boronation/oxidation sequence has been developed. Oxidation of the generated alkynyl boronate affords the corresponding ketene intermediate, which is trapped by the adjacent hydroxy group to furnish the γ-lactone. We have optimized the conditions as well as examined the substrate scope and synthetic applications of this efficient one-pot lactonization.

Synthesis, crystal structure and spectroscopic and Hirshfeld surface analysis of 4-hy-droxy-3-meth-oxy-5-nitro-benzaldehyde.

The title compound, C8H7NO5, is planar with an r.m.s. deviation for all non-hydrogen atoms of 0.018 Å. An intra-molecular O-H⋯O hydrogen bond involving the adjacent hy-droxy and nitro groups forms an S(6) ring motif. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the bc plane. The layers are linked by a further C-H⋯O hydrogen bond, forming slabs, which are linked by C=O⋯π inter-actions, forming a three-dimensional supra-molecular structure. Hirshfeld surface analysis was used to investigate inter-molecular inter-actions in the solid state. The mol-ecule was also characterized spectroscopically and its thermal stability investigated by differential scanning calorimetry and by thermogravimetric analysis.

A Curcumin Degradation Product, 7-Norcyclopentadione, Formed by Aryl Migration and Loss of a Carbon from the Heptadienedione Chain.

Evidence that anti-inflammatory and other biological effects of curcumin may at least in part be mediated by its metabolites underscores the importance of identifying novel transformation products. Spontaneous degradation of curcumin in buffer pH 7.5 results mainly in dioxygenated products with a characteristic cyclopentadione ring composed of carbons 2 through 6 of the former heptadienedione chain. When analyzing degradation reactions of 4'- O-methylcurcumin, a product was identified missing one of the terminal carbons of the heptadienedione moiety while containing a cyclopentadione ring and adjacent hydroxy group typical of curcumin degradation products. Analysis of curcumin autoxidation reactions showed formation of an analogous compound, 7-norcyclopentadione, a degradation product exhibiting net loss of a carbon and gain of an oxygen atom. Removal of the carbon is proposed to occur via a peroxide-linked curcumin dimer in conjunction with radical-mediated 1,2-aryl migration of a guaiacol moiety. Oxidation reactions of demethoxycurcumin gave demethoxy-7-norcyclopentadione, whereas an analogous product was not observed from bis-demethoxycurcumin. Incubation of RAW264.7 macrophage-like cells with curcumin showed the presence of 7-norcyclopentadione, the formation of which was not increased upon activation of the cells with 12- O-tetradecanoylphorbol-13-acetate . 7-Norcyclopentadione is a novel type of degradation product that is most likely formed via autoxidative processes when cells are incubated with curcumin.

Site-Selective, Copper-Mediated O-Arylation of Carbohydrate Derivatives.

Site-selective functionalization of hydroxy groups in sugar derivatives is a major challenge in carbohydrate synthesis. Methods for achieving this goal will provide efficient access to new sugar-derived chemical building blocks and will facilitate the preparation or late-stage modification of complex oligosaccharides for applications in glycobiology research and drug discovery. Here, we describe site-selective, copper-promoted couplings of boronic acids with carbohydrate derivatives. These reactions generate sugar-derived aryl ethers, a structural class that is challenging to generate by other means and has not previously been accessed in a site-selective fashion. Experimental evidence and computational modeling suggest that the formation of a sugar-derived boronic ester intermediate is crucial to the selectivity of these processes, accelerating the arylation of an adjacent hydroxy group. The results demonstrate how the interactions of sugars with boron compounds can be combined with transition metal catalysis to achieve new chemical reactivity.

ChemInform Abstract: An Efficient Synthesis and Regioselective Hydrogenolysis of Dioxolane‐Type of Carbohydrates.

Abstract Carbohydrates, inexpensive chiral sources, are very useful for many syntheses of chiral bioactive compounds. We have chosen to synthesize benzyl α- d -mannofuranosides and d -lyxofuranosides with dioxolane-type, 2,3-O-isopentylidene and 2,3-O-benzylidene acetals from d -mannose. Interestingly, we have discovered new knowledge about the cleavage of dioxolane-type using two catalysts, Cu(OTf)2/BH3·THF and TiCl4/Et3SiH. The results showed that the regioselectivity of the benzylidene acetal ring opening was affected by the adjacent hydroxy (OH) group and was not directed by the stereochemistry of the acetal center. The substrates containing OH groups at position 5 can be cleaved by Cu(OTf)2/BH3·THF in tetrahydrofuran to exclusively provide the 2-O-benzyl-3-hydroxy compounds. When the substrates bore the OH group at position 6, using TiCl4/Et3SiH in dichloromethane gave a similar pattern. If the substrates lacked the OH group at position 5 or 6, the reactions did not proceed or gave low selectivity. Our discovery is very useful for dioxolane-type ring opening of carbohydrate synthesis.

An efficient synthesis and regioselective hydrogenolysis of dioxolane-type of carbohydrates

Carbohydrates, inexpensive chiral sources, are very useful for many syntheses of chiral bioactive compounds. We have chosen to synthesize benzyl α-d-mannofuranosides and d-lyxofuranosides with dioxolane-type, 2,3-O-isopentylidene and 2,3-O-benzylidene acetals from d-mannose. Interestingly, we have discovered new knowledge about the cleavage of dioxolane-type using two catalysts, Cu(OTf)2/BH3·THF and TiCl4/Et3SiH. The results showed that the regioselectivity of the benzylidene acetal ring opening was affected by the adjacent hydroxy (OH) group and was not directed by the stereochemistry of the acetal center. The substrates containing OH groups at position 5 can be cleaved by Cu(OTf)2/BH3·THF in tetrahydrofuran to exclusively provide the 2-O-benzyl-3-hydroxy compounds. When the substrates bore the OH group at position 6, using TiCl4/Et3SiH in dichloromethane gave a similar pattern. If the substrates lacked the OH group at position 5 or 6, the reactions did not proceed or gave low selectivity. Our discovery is very useful for dioxolane-type ring opening of carbohydrate synthesis.

N-Hexyl-3,4-dihydroxybenzamide

In the title compound, C13H19NO3, the hexyl chain has en extended conformation and its mean plane is inclined to the benzene ring by 3.29 (10)°. There is a short O—H...O contact in the molecule involving the adjacent hydroxy groups. In the crystal, molecules are linkedviaO—H...O and N—H...O hydrogen bonds, forming slabs parallel to (001). Within the slabs, there are also C—H...O hydrogen bonds and C—H...π interactions present.

Reason for the High Solubility of Chemically Modified Poly(vinyl alcohol)s in Aqueous Solution

Partially chemically modified poly(vinyl alcohol) synthesized via random introduction of a diol-type monomer (mPVA) shows much higher solubility in water than normal homo poly(vinyl alcohol) (PVA). To clarify the reason for the high solubility of mPVA, we investigated the temperature dependencies of the hydration numbers per hydroxy group (mOH) for mPVA at various diol-type monomer contents from x = 0 (PVA) to 0.12 using extremely high frequency dielectric relaxation measurements up to 50 GHz over a temperature range from 10 to 70 °C. The values of mOH for mPVA in the temperature range below 20 °C looked constant and increased from 2.4 to 3.4 with increasing x. Above 20 °C, the values of mOH decreased with increasing temperature and approached a constant value close to unity above 70 °C irrespective of x. Although the random introduction of the diol-type monomer into the mPVA backbones effectively increased the mOH values, broad dehydration was commonly observed at approximately 40 °C irrespective of the x value. It is likely that the presence of the diol-type monomers in the polymer backbone considerably disturbs the highly developed sequential intramolecular hydrogen bonding between adjacent hydroxy groups in the normal homo PVA.

Crystal Structures of 1-Benzoyl-2-hydroxy-7-methoxynaphthalene Analogues: Dimeric Features of the Molecular Packing

Molecular alignments of 1-aroyl-2-hydroxy-7-methoxynaphthalene analogues are classified into two groups, i.e., molecular stacking standing one behind another and dimeric aggregates. In single molecular structures, the 1-aroyl-2-hydroxy-7-methoxynaphthalene analogues show apparently same spatial organizations. The carbonyl groups in these molecules form intramolecular O–H…O=C hydrogen bonds with the adjacent hydroxy groups, affording six-membered cyclic structures. The aroyl groups constrained by the intramolecular hydrogen bonds essentially induce dimeric aggregates via formation of a pair of inter molecular O–H…O=C hydrogen bonds. When interactions led by the substituents of the benzene rings reduce the stability by the inter molecular O–H…O=C hydrogen bonds, the molecular packing should turn one-behind-one type piling.

The zwitterionic structure of 2-hydroxy-4-[(2-hydroxybenzylidene)amino]benzoic acid

The title compound, C₁₄H₁₁NO₄, exists in the solid phase in the zwitterionic form, 2-{[(4-carboxy-3-hydroxyphenyl)iminiumyl]methyl}phenolate, with the H atom from the phenol group on the 2-hydroxybenzylidene ring transferred to the imine N atom, resulting in a strong intramolecular N-H∙∙∙O hydrogen bond between the iminium H atom and the phenolate O atom, forming a six-membered hydrogen-bonded ring. In addition, there is an intramolecular O-H∙∙∙O hydrogen bond between the carboxylic acid group and the adjacent hydroxy group of the other ring, and an intermolecular C-H∙∙∙O contact involving the phenol group and the C-H group adjacent to the imine bond, connecting the molecules into a two-dimensional network in the (103) plane. π-π stacking interactions result in a three-dimensional network. This study is important because it provides crystallographic evidence, supported by IR data, for the iminium zwitterionic form of Schiff bases.

Hydration/Dehydration Behavior of Polyalcoholic Compounds Governed by Development of Intramolecular Hydrogen Bonds

Hydration/dehydration behavior of polyalcoholic compounds with a rigid cyclohexane-type aliphatic molecular frame, such as 1,4-cyclohexanediol (ch(OH)2), 1α,3α,5α-cyclohexanetriol (cis-phloroglucitol, ch(OH)3), and cis-1,2,3,5-trans-4,6-cyclohexanehexaol (myo-inositol, ch(OH)6) was investigated using extremely high-frequency dielectric relaxation measurements up to 50 GHz over a temperature range from 10 to 70 °C. The temperature dependencies of hydration numbers per hydroxy group (mOH) in the polyalcoholic compounds were determined. Although the obtained mOH value was ca. 5 in a temperature range lower than 30 °C, it decreased and approached to ca. 3 with increasing temperature for ch(OH)2 and ch(OH)3, in which hydroxy groups hardly form intramolecular hydrogen bonds due to separations between them. This temperature-dependent hydration/dehydration behavior is characteristic of isolated hydroxy groups without intramolecular hydrogen bond formation. On the other hand, a constant mOH value of ca. 1 was observed irrespective of temperature for ch(OH)6. Because all the separations between adjacent hydroxy groups in ch(OH)6 are proper for (circular type) intramolecular hydrogen bond formation, the obtained temperature-independent small mOH value resulted from an inherent feature of intramolecularly hydrogen bonded hydroxy groups.

Effect of Additives on L-Proline Catalyzed Direct Asymmetric Aldol Reactions

The direct asymmetric aldol reaction of aromatic aldehydes with acetone catalyzed by L-proline was accelerated by the addition of diols or diphenols. The use of additives decrease the amount of L-proline needed and allowed the use of solvent free conditions. Catechol with two adjacent hydroxy groups on aromatic ring was the most efficient additive. Under the optimized conditions, 5 mol% L-proline with 1 mol% catechol gave excellent chiral selectivity (80% ee value) with > 90% yield, which was higher than that obtained using 30 mol% L-proline without an additive. Computations indicated that the additive promoted the reaction by an intermolecular hydrogen bond between the hydrogen of the hydroxyl group and the oxygen of the carbonyl group, which activated the carbonyl group of the aldehyde. Catechol with two adjacent hydroxyl groups on the aromatic ring can form two hydrogen bonds with the oxygen of the carbonyl group on the corresponding aldehyde. Therefore, the combination of L-proline and catechol was very efficient in catalyzing the direct asymmetric aldol reaction and gave a high yield in a short time. 在 L-脯氨酸催化的芳香醛与丙酮直接不对称 aldol 反应体系中添加二醇或二酚类助剂可有效提高反应活性. 助剂的使用降低了该反应体系中 L-脯氨酸的用量. 特别是以邻苯二酚为助剂时, 最佳反应条件下, 仅用 5 mol% L-脯氨酸与 1 mol% 助剂催化 2-硝基苯甲醛与丙酮直接不对称 aldol 反应, aldol 产物产率高达 90%, 对映选择性为 80%. 该反应产率比未加助剂条件下, L-脯氨酸用量为 30 mol% 时的反应产率高. 采用量子化学计算研究了助剂对该反应的促进作用. 结果表明, 助剂可与芳香醛的醛基形成氢键, 从而活化醛基, 提高反应效率. 邻苯二酚结构中相邻的羟基能与底物芳香醛羰基的氧原子形成双氢键, 大大活化了底物芳香醛的羰基. 因此, 该助剂可有效促进 L-脯氨酸催化剂的直接不对称 aldol 反应. Cheap catechol promoted the L-proline catalyzed aldol reaction efficiently through hydrogen-bonds interaction, which decreased the amount of L-proline and increased the yield of aldol products.

(E)-Isopentyl 3-(3,4-dihydroxyphenyl)acrylate

The title compound, C14H18O4, a derivative of caffeic acid, has an E configuration about the C=C bond. The benzene ring is almost coplanar with the C=C—C(O)—O—C linker [maximum deviation = 0.050 (2) Å], making a dihedral angle of only 4.53 (2)°. In the mol­ecule, the adjacent hy­droxy groups form an O—H⋯O inter­action. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, generating a chain propagating in the [110] direction.

(2Z)-1-(5-Hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3-(4-methoxyanilino)but-2-en-1-one

The central residue in the title compound, C21H21N3O3, is close to planar (r.m.s. deviation = 0.0753 Å for all non-H atoms from OH to NH inclusive): the hy­droxy, amino and carbonyl groups all lie to the same side of the mol­ecule (the conformation about the ethene bond is Z), facilitating the formation of intra­molecular O—H⋯O and N—H⋯O hydrogen bonds that close S(6) rings. However, overall the mol­ecule is twisted as the terminal aromatic rings are not coplanar with the central plane [dihedral angles = 20.55 (5) and 80.90 (4)° for the N-bound phenyl ring and the meth­oxy­benzene ring, respectively]. The dihedral angle between the rings is 82.14 (7)°. Supra­molecular layers in the ac plane mediated by C—H⋯π inter­actions are found in the crystal.

Tris(hydroxypropyl)phosphine Oxide: A Chiral Three-Dimensional Material with Nonlinear Optical Properties

The achiral C_(3v) organic phosphine tris(hydroxypropyl)phosphine oxide (1) crystallizes in the unusual chiral hexagonal space group P6_3. The structure is highly ordered because each phosphine oxide moiety forms three hydrogen bonds with adjacent hydroxy groups from three different molecules. The properties of the crystals and the presence of hydrogen bonding interactions were investigated using single crystal Raman spectroscopy. The crystals show nonlinear optical properties and are capable of efficient second harmonic generation.

Ring Expansion of 2‐(α‐Hydroxyalkyl)azetidines: A Synthetic Route to Functionalized Pyrrolidines

AbstractA series of 2‐(α‐hydroxyalkyl)azetidines synthesized from enantiomerically pure β‐amino alcohols and presenting various patterns both on the four‐membered ring and on the adjacent hydroxy group were treated with either thionyl chloride or methanesulfonyl chloride in the presence of triethylamine. The thus‐prepared 2‐(α‐chloro‐ or α‐methanesulfonyloxyalkyl)azetidines were shown to rearrange stereospecifically into 3‐(chloro‐ or methanesulfonyloxy)pyrrolidines. When this rearrangement is conducted in the presence of an added nucleophile (NaN3, KCN, KOH, or NaOAc), the produced pyrrolidine incorporates the added nucleophile at C‐3 stereospecifically. The relative configuration of the substituents in the formed pyrrolidines is consistent with a mechanism involving the formation of an intermediate bicyclic aziridinium ion, which is opened regioselectively at the bridgehead carbon atom. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Rate acceleration of phosphoric acid-catalyzed Diels-Alder reaction by internal hydrogen-bonding of adjacent hydroxy group

The Brønsted acid-catalyzed Diels-Alder reaction was examined. Phosphoric acids were effective Brønsted acids for the Diels-Alder reaction of cyclohexadienones and activated by the internal hydrogen-bonding of the adjacent hydroxy group.