Synthesis of Monofunctionalized Calix[5]arenes

Synthesis ◽  
2017 ◽  
Vol 50 (03) ◽  
pp. 676-684 ◽  
Author(s):  
Arne Lützen ◽  
Björn Ingenfeld ◽  
Steffen Straub ◽  
Christopher Frömbgen
Keyword(s):  
Hydrogen Bonds ◽  
Functional Groups ◽  
Functional Group ◽  
Building Blocks ◽  
Cone Conformation ◽  
Oh Groups ◽  
Tert Butyl ◽  
Fragment Condensation ◽  
Molecular Architectures ◽  
Phenolic Oh Groups

Seven OH-free and O-permethylated monofunctionalized calix[5]arenes carrying either additional methyl or tert-butyl groups are prepared following fragment condensation protocols. This strategy proves to be superior to previous approaches. Calix[5]arenes with free OH groups all adopt a cone conformation stabilized by a seam of hydrogen bonds at the lower rim. Post-condensation modifications, i.e., methylation of phenolic OH groups or functional group interconversions can also be achieved. Bulky tert-butyl groups are also found to stabilize the cone conformations of O-methylated compounds. These compounds offer versatile functional groups that make these concave molecules interesting building blocks for the synthesis of more sophisticated molecular architectures.

Mechanical Properties of Graphene Oxide/Polyvinyl Alcohol Composite Film

2017 ◽  
Vol 25 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Tao Cheng-an ◽  
Zhang Hao ◽  
Wang Fang ◽  
Zhu Hui ◽  
Zou Xiaorong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Graphene Oxide ◽  
Hydrogen Bonds ◽  
Polyvinyl Alcohol ◽  
Composite Film ◽  
Functional Groups ◽  
Failure Strain ◽  
Oh Groups ◽  
Enhancement Mechanism

Graphene oxide (GO) was served as mechanical strengthening to prepare GO/Polyvinyl Alcohol(PVA) composite film. This was accomplished in order to explore the influence of contents of GO on the tensile strength and failure strain of GO/PVA composite film. The results showed that as the GO content increased, the tensile strength of the composite film became greater rapidly at first, and then decreased gradually. When the GO content was 20%, the film had its maximum tensile strength (59.6 MPa). This is over 500% of the tensile strength of pure PVA film. The failure strain of GO/PVA composite film decreased rapidly as the GO content increased. The enhancement mechanism of the composite can be explained by the existence of multi-hydrogen bonds between the hydroxyl (-OH) groups of PVA and oxygen-containing functional groups of GO.

Complexes of halloysite with organic compounds

Clay Minerals ◽  
1971 ◽  
Vol 9 (2) ◽  
pp. 153-166 ◽  
Author(s):  
R. M. Carr ◽  
Hwa Chih
Keyword(s):  
Hydrogen Bonds ◽  
Functional Groups ◽  
Organic Compounds ◽  
Organic Molecules ◽  
Functional Group ◽  
Particle Morphology ◽  
Organic Complexes ◽  
Insufficient Knowledge ◽  
Quantitative Evaluations

AbstractMore than twenty new organic complexes of halloysite have been prepared and one hundred and twenty-seven compounds were tested. Results are compared with those of earlier studies and use is made of recent findings concerning particle morphology and interstratification effects to interpret the results. The compounds which form complexes with halloysite are polar, and are usually either acids or bases. Their molecules usually contain two functional groups (preferably —OH and/or —NH2), are relatively small and have one functional group per two carbon atoms, but do not usually include cyclic or aromatic types. The best explanation of the existence of these metastable complexes seems to lie in the ability of some organic molecules to form hydrogen bonds with the halloysite structure, about which insufficient knowledge is available to allow quantitative evaluations to be made.

Synthesis and Crystal Structure of Calix[4]arene Derivative Containing 1,3-Diketo Moieties

2019 ◽  
Vol 16 (9) ◽  
pp. 735-739
Author(s):  
Xuemei Xu ◽  
Zaigang Luo ◽  
Chao Ma
Keyword(s):  
Crystal Structure ◽  
Diffraction Analysis ◽  
Crystal Packing ◽  
X Ray Diffraction ◽  
Cone Conformation ◽  
Synthesis And Crystal Structure ◽  
Arene Derivative ◽  
Oh Groups ◽  
X Ray ◽  
Phenolic Oh Groups

The synthesis of the calix[4]arene derivative containing 1,3-diketo moieties via direct Claisen condensation without protection of the unsubstituted phenolic OH groups is reported. Single crystal X-ray diffraction analysis reveals that the calix unit to be in a cone conformation incorporating two 1,3-diketo subunits disposed in alternate position at the lower rim. And the crystal packing reveals that the overall packing of the complex is staggered anti-parallelly.

MICROWAVE PYROLYSIS ASSISTED WITH CARBON BASED ABSORBENT: AN OVERVIEW

2015 ◽  
Vol 76 (10) ◽  
Author(s):  
Syarifah Nor Faizah Syed Abdul Rahman ◽  
Norazah Abd Rahman ◽  
Siti Shawalliah Idris ◽  
Noor Fitrah Abu Bakar ◽  
Roslan Mokhtar
Keyword(s):  
Hydrogen Bonds ◽  
Small Molecules ◽  
Functional Groups ◽  
Van Der Waals Forces ◽  
Building Blocks ◽  
Supramolecular Interactions ◽  
Supramolecular Polymer ◽  
Gel Formation ◽  
Microwave Pyrolysis ◽  
Gel Phase

Over recent years, there has been an explosive growth of interest in the development of novel gel-phase materials based on small molecules. It has been recognised that an effective gelator should possess functional groups that interact with each other via temporal associative forces. This process leads to the formation of supramolecular polymer-like structures, which then aggregated further hence, gelating the solvent. Supramolecular interactions between building blocks that enable gel formation include hydrogen bonds, interactions, solvatophobic effects and van der Waals forces.  

Differentiation and Functionalization of Adjacent, Remote C–H Bonds

2019 ◽  
Author(s):  
Hang Shi ◽  
Lu Yi ◽  
Jiang Weng ◽  
Katherine Bay ◽  
Xiangyang Chen ◽  
...  
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Hydrocinnamic Acid ◽  
Molecular Architectures ◽  
Site Selective ◽  
Developing Strategies

<p>Site-selective functionalizations of C–H bonds will ultimately afford chemists transformative tools for editing and constructing complex molecular architectures<sup>1-4</sup>. Towards this goal, developing strategies to activate C–H bonds that are distal from a functional group is essential<sup>4-6</sup>. In this context, distinguishing remote C–H bonds on adjacent carbon atoms is an extraordinary challenge due to the lack of electronic or steric bias between the two positions. Herein, we report the design of a catalytic system leveraging a remote directing template and a transient norbornene mediator to selectively activate a previously inaccessible remote C–H bond that is one bond further away. The generality of this approach has been demonstrated with a range of heterocycles, including a complex anti-leukemia agent, and hydrocinnamic acid substrates.</p>

A Practical and General Approach to the Late-Stage Functionalization of Complex Sulfonamides

2019 ◽  
Author(s):  
Patrick Fier ◽  
Kevin M. Maloney
Keyword(s):  
Functional Groups ◽  
Late Stage ◽  
Building Blocks ◽  
Pharmaceutical Compounds ◽  
Stage Conversion

Herein we describe the development and application of a method for the mild, late-stage conversion of primary sulfonamides to several other other functional groups. These reactions occur via initial reductive deamination of sulfonamides to sulfinates via an NHC-catalyzed reaction of transiently formed <i>N</i>-sulfonylimines. The method described here is tolerant of nearly all common functional groups, as exemplified by the late-stage derivatization of several complex pharmaceutical compounds. Based on the prevalence of sulfonamide-containing drugs and building blocks, we have developed a method to enable sulfonamides to be applied as versatile synthetic handles for synthetic chemsitry.

A Practical and General Approach to the Late-Stage Functionalization of Complex Sulfonamides

2019 ◽  
Author(s):  
Patrick Fier ◽  
Kevin M. Maloney
Keyword(s):  
Functional Groups ◽  
Late Stage ◽  
Building Blocks ◽  
Pharmaceutical Compounds ◽  
Stage Conversion

Herein we describe the development and application of a method for the mild, late-stage conversion of primary sulfonamides to several other other functional groups. These reactions occur via initial reductive deamination of sulfonamides to sulfinates via an NHC-catalyzed reaction of transiently formed <i>N</i>-sulfonylimines. The method described here is tolerant of nearly all common functional groups, as exemplified by the late-stage derivatization of several complex pharmaceutical compounds. Based on the prevalence of sulfonamide-containing drugs and building blocks, we have developed a method to enable sulfonamides to be applied as versatile synthetic handles for synthetic chemsitry.

Statistical Analysis of the Relationship Between Antioxidant Activity and the Structure of Flavonoid Compounds

2019 ◽  
Vol 70 (9) ◽  
pp. 3103-3107 ◽  
Author(s):  
Ioana Glevitzky ◽  
Gabriela Alina Dumitrel ◽  
Mirel Glevitzky ◽  
Bianca Pasca ◽  
Pavel Otrisal ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Antioxidant Activities ◽  
Basic Structure ◽  
Oh Groups ◽  
Flavonoid Compounds ◽  
Chi Squared ◽  
Potential Link ◽  
Van Der Waals Surface ◽  
The Relationship ◽  
Phenolic Oh Groups

Using different methods of statistics, this paper aims to highlight the potential link between the antioxidant activity of flavonoids and the corresponding molecular descriptors. By calculating the descriptors (van der Waals surface (A), molar volume (V), partition coefficient (LogP), refractivity (R), polarizability (a), forming heat (Hformation), hydration energy (Ehidr), the dipole moment (mt)), together with antioxidant activities (RSA) calculated or taken from the literature, number of phenolic -OH groups and the presence (2) or absence (1) of C2=C3 double bond) for 29 flavonoid compounds and by intercorrelation between the studied parameters, the link between the number of phenolic groups grafted to the basic structure of flavonoids and their antioxidant activity was confirmed. Simultaneously, by using the chi-squared test and the intercorrelations matrix, a satisfactorily correlation coefficient (r2=0.5678; r=0.7536) between the structure of the flavonoids and their activity was obtained, fact that confirms the correlation of the antioxidant activity with the number of -OH phenolic groups.

scholarly journals Non-Enzymatic Desymmetrization Reactions in Aqueous Media

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 720
Author(s):  
Satomi Niwayama
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Functional Groups ◽  
Organic Compounds ◽  
Recent Progress ◽  
Aqueous Media ◽  
Building Blocks ◽  
Organic Reactions ◽  
Environmentally Benign ◽  
Enzymatic Desymmetrization

Symmetric organic compounds are generally obtained inexpensively, and therefore they can be attractive building blocks for the total synthesis of various pharmaceuticals and natural products. The drawback is that discriminating the identical functional groups in the symmetric compounds is difficult. Water is the most environmentally benign and inexpensive solvent. However, successful organic reactions in water are rather limited due to the hydrophobicity of organic compounds in general. Therefore, desymmetrization reactions in aqueous media are expected to offer versatile strategies for the synthesis of a variety of significant organic compounds. This review focuses on the recent progress of desymmetrization reactions of symmetric organic compounds in aqueous media without utilizing enzymes.

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