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21 pages, 27734 KiB

Open AccessArticle

¹³C NMR Spectroscopic Studies of Intra- and Intermolecular Interactions of Amino Acid Derivatives and Peptide Derivatives in Solutions

by Yoshikazu Hiraga, Saori Chaki, Yuri Uyama, Ryosuke Hoshide, Takumi Karaki, Daisuke Nagata, Kanji Yoshimoto and Satomi Niwayama

Organics 2022, 3(1), 38-58; https://doi.org/10.3390/org3010003 - 9 Feb 2022

Viewed by 4435

Abstract

¹³C NMR spectroscopic investigations were conducted for various amino acid derivatives and peptides. It was observed that ¹³C NMR chemical shifts of the carbonyl carbons are correlated with the solvent polarities, but the extent depends on the structures. The size of [...] Read more.

¹³C NMR spectroscopic investigations were conducted for various amino acid derivatives and peptides. It was observed that ¹³C NMR chemical shifts of the carbonyl carbons are correlated with the solvent polarities, but the extent depends on the structures. The size of the functional groups and inter- and intra-molecular hydrogen bonding appear to be the major contributors for this tendency. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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9 pages, 899 KiB

Open AccessArticle

Micellar Suzuki Cross-Coupling between Thiophene and Aniline in Water and under Air

by Dawod Yousif, Silvia Tombolato, Elmehdi Ould Maina, Riccardo Po, Paolo Biagini, Antonio Papagni and Luca Vaghi

Organics 2021, 2(4), 415-423; https://doi.org/10.3390/org2040025 - 16 Dec 2021

Cited by 2 | Viewed by 3427

Abstract

The Suzuki–Miyaura cross-coupling reaction plays a fundamental role in modern synthetic organic chemistry, both in academia and industry. For this reason, scientists continue to search for new, more effective, cheaper and environmentally friendly procedures. Recently, micellar synthetic chemistry has been demonstrated to be [...] Read more.

The Suzuki–Miyaura cross-coupling reaction plays a fundamental role in modern synthetic organic chemistry, both in academia and industry. For this reason, scientists continue to search for new, more effective, cheaper and environmentally friendly procedures. Recently, micellar synthetic chemistry has been demonstrated to be an excellent strategy for achieving chemical transformations in a more efficient way, thanks to the creation of nanoreactors in aqueous environments using selected surfactants. In particular, the cheap and commercially available surfactant Kolliphor EL (a polyethoxylated castor oil derivative) has been used with success to achieve metal-catalyzed transformations in water with high yields and short reaction times, with the advantage of using air-sensitive catalysts without the need for inert atmosphere. In this work, the Kolliphor EL methodology was applied to the Suzuki cross-coupling reaction between thiophene and aniline, using the highly effective catalyst Pd(dtbpf)Cl₂. The cross-coupling products were achieved at up to 98% yield, with reaction times of up to only 15 min, working at room temperature and without the need for inert atmosphere. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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11 pages, 1306 KiB

Open AccessArticle

A Sustainable Improvement of ω-Bromoalkylphosphonates Synthesis to Access Novel KuQuinones

by Mattia Forchetta, Valeria Conte, Giulia Fiorani, Pierluca Galloni and Federica Sabuzi

Organics 2021, 2(2), 107-117; https://doi.org/10.3390/org2020010 - 3 Jun 2021

Cited by 5 | Viewed by 4079

Abstract

Owing to the attractiveness of organic phosphonic acids and esters in the pharmacological field and in the functionalization of conductive metal-oxides, the research of effective synthetic protocols is pivotal. Among the others, ω-bromoalkylphosphonates are gaining particular attention because they are useful building [...] Read more.

Owing to the attractiveness of organic phosphonic acids and esters in the pharmacological field and in the functionalization of conductive metal-oxides, the research of effective synthetic protocols is pivotal. Among the others, ω-bromoalkylphosphonates are gaining particular attention because they are useful building blocks for the tailored functionalization of complex organic molecules. Hence, in this work, the optimization of Michaelis–Arbuzov reaction conditions for ω-bromoalkylphosphonates has been performed, to improve process sustainability while maintaining good yields. Synthesized ω-bromoalkylphosphonates have been successfully adopted for the synthesis of new KuQuinone phosphonate esters and, by hydrolysis, phosphonic acid KuQuinone derivatives have been obtained for the first time. Considering the high affinity with metal-oxides, KuQuinones bearing phosphonic acid terminal groups are promising candidates for biomedical and photo(electro)chemical applications. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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7 pages, 785 KiB

Open AccessArticle

Pd-Based Polysaccharide Hydrogels as Heterogeneous Catalysts for Oxidation of Aromatic Alcohols

by Oshrat Levy-Ontman, Eliraz Stamker, Vital Mor and Adi Wolfson

Organics 2021, 2(1), 50-56; https://doi.org/10.3390/org2010005 - 17 Mar 2021

Cited by 2 | Viewed by 9347

Abstract

Immobilization of Pd(OAc)₂(TPPTS)₂ in various renewable polysaccharides hydrogels, yielded heterogeneous catalysts that were successfully used, for the first time, in the aerobic oxidation of benzylic alcohol. The new catalysts were easily removed from the reaction mixture and recycled with some [...] Read more.

Immobilization of Pd(OAc)₂(TPPTS)₂ in various renewable polysaccharides hydrogels, yielded heterogeneous catalysts that were successfully used, for the first time, in the aerobic oxidation of benzylic alcohol. The new catalysts were easily removed from the reaction mixture and recycled with some loss of activity. Among all tested polysaccharides, iota-carrageenan was found to be the most suitable support, using calcium chloride as a gelation agent. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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9 pages, 3118 KiB

Open AccessFeature PaperArticle

Esterifications with 2-(Trimethylsilyl)ethyl 2,2,2-Trichloroacetimidate

by Wenhong Lin, Shea T. Meyer, Shawn Dormann and John D. Chisholm

Organics 2021, 2(1), 17-25; https://doi.org/10.3390/org2010002 - 4 Feb 2021

Cited by 1 | Viewed by 4719

Abstract

2-(Trimethylsilyl)ethyl 2,2,2-trichloroacetimidate is readily synthesized from 2-trimethylsilylethanol in high yield. This imidate is an effective reagent for the formation of 2-trimethylsilylethyl esters without the need for an exogenous promoter or catalyst, as the carboxylic acid substrate is acidic enough to promote ester formation [...] Read more.

2-(Trimethylsilyl)ethyl 2,2,2-trichloroacetimidate is readily synthesized from 2-trimethylsilylethanol in high yield. This imidate is an effective reagent for the formation of 2-trimethylsilylethyl esters without the need for an exogenous promoter or catalyst, as the carboxylic acid substrate is acidic enough to promote ester formation without an additive. A deuterium labeling study indicated that a β-silyl carbocation intermediate is involved in the transformation. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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Review

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17 pages, 7532 KiB

Open AccessReview

Synthesis of 1-Trifluorometylindanes and Close Structures: A Mini Review

by Olesya V. Khoroshilova and Aleksander V. Vasilyev

Organics 2021, 2(4), 348-364; https://doi.org/10.3390/org2040019 - 8 Oct 2021

Cited by 7 | Viewed by 2908

Abstract

This review describes methods for the synthesis of 1-trifluomethylindanes and close structures, which are still quite rare and scarcely available compounds. There are two main approaches to obtain 1-CF₃-indanes. The first one is the construction of an indane system from CF [...] Read more.

This review describes methods for the synthesis of 1-trifluomethylindanes and close structures, which are still quite rare and scarcely available compounds. There are two main approaches to obtain 1-CF₃-indanes. The first one is the construction of an indane system from CF₃ precursors; the main methods are acid-mediated Friedel–Crafts cyclization, transition metal-catalyzed [3+2] annulation, and free-radical transformations. The second approach is the trifluoromethylation of a ready-made indane core by various CF₃ sources, such as Ruppert–Prakash or Togni reagents. Many of these synthetic procedures possess high regio- and stereo-selectivity, allowing the preparation of unique 1-CF₃-indane structures. In recent years, great attention has been paid to the synthesis of 1-CF₃-indanes, due to the discovery of important biologically active properties for these compounds. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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11 pages, 2628 KiB

Open AccessReview

Recent Advances in the Synthesis of Piperazines: Focus on C–H Functionalization

by Carolina Durand and Michal Szostak

Organics 2021, 2(4), 337-347; https://doi.org/10.3390/org2040018 - 8 Oct 2021

Cited by 16 | Viewed by 8030

Abstract

Piperazine ranks as the third most common nitrogen heterocycle in drug discovery, and it is the key component of several blockbuster drugs, such as Imatinib (also marketed as Gleevec) or Sildenafil, sold as Viagra. Despite its wide use in medicinal chemistry, the structural [...] Read more.

Piperazine ranks as the third most common nitrogen heterocycle in drug discovery, and it is the key component of several blockbuster drugs, such as Imatinib (also marketed as Gleevec) or Sildenafil, sold as Viagra. Despite its wide use in medicinal chemistry, the structural diversity of piperazines is limited, with about 80% of piperazine-containing drugs containing substituents only at the nitrogen positions. Recently, major advances have been made in the C–H functionalization of the carbon atoms of the piperazine ring. Herein, we present an overview of the recent synthetic methods to afford functionalized piperazines with a focus on C–H functionalization. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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113 pages, 10965 KiB

Open AccessFeature PaperReview

Design, Synthesis, and Utility of Defined Molecular Scaffolds

by Daisuke Sato, Zhiyuan Wu, Hikaru Fujita and Jonathan S. Lindsey

Organics 2021, 2(3), 161-273; https://doi.org/10.3390/org2030013 - 11 Jul 2021

Cited by 24 | Viewed by 8278

Abstract

A growing theme in chemistry is the joining of multiple organic molecular building blocks to create functional molecules. Diverse derivatizable structures—here termed “scaffolds” comprised of “hubs”—provide the foundation for systematic covalent organization of a rich variety of building blocks. This review encompasses 30 [...] Read more.

A growing theme in chemistry is the joining of multiple organic molecular building blocks to create functional molecules. Diverse derivatizable structures—here termed “scaffolds” comprised of “hubs”—provide the foundation for systematic covalent organization of a rich variety of building blocks. This review encompasses 30 tri- or tetra-armed molecular hubs (e.g., triazine, lysine, arenes, dyes) that are used directly or in combination to give linear, cyclic, or branched scaffolds. Each scaffold is categorized by graph theory into one of 31 trees to express the molecular connectivity and overall architecture. Rational chemistry with exacting numbers of derivatizable sites is emphasized. The incorporation of water-solubilization motifs, robust or self-immolative linkers, enzymatically cleavable groups and functional appendages affords immense (and often late-stage) diversification of the scaffolds. Altogether, 107 target molecules are reviewed along with 19 syntheses to illustrate the distinctive chemistries for creating and derivatizing scaffolds. The review covers the history of the field up through 2020, briefly touching on statistically derivatized carriers employed in immunology as counterpoints to the rationally assembled and derivatized scaffolds here, although most citations are from the past two decades. The scaffolds are used widely in fields ranging from pure chemistry to artificial photosynthesis and biomedical sciences. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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19 pages, 5287 KiB

Open AccessReview

Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

by Keith Smith and Gamal A. El-Hiti

Organics 2021, 2(3), 142-160; https://doi.org/10.3390/org2030012 - 8 Jul 2021

Cited by 2 | Viewed by 4655

Abstract

para-Selective processes for the chlorination of phenols using sulphuryl chloride in the presence of various sulphur-containing catalysts have been successfully developed. Several chlorinated phenols, especially those derived by para-chlorination of phenol, ortho-cresol, meta-cresol, and meta-xylenol, are of significant [...] Read more.

para-Selective processes for the chlorination of phenols using sulphuryl chloride in the presence of various sulphur-containing catalysts have been successfully developed. Several chlorinated phenols, especially those derived by para-chlorination of phenol, ortho-cresol, meta-cresol, and meta-xylenol, are of significant commercial importance, but chlorination reactions of such phenols are not always as regioselective as would be desirable. We, therefore, undertook the challenge of developing suitable catalysts that might promote greater regioselectivity under conditions that might still be applicable for the commercial manufacture of products on a large scale. In this review, we chart our progress in this endeavour from early studies involving inorganic solids as potential catalysts, through the use of simple dialkyl sulphides, which were effective but unsuitable for commercial application, and through a variety of other types of sulphur compounds, to the eventual identification of particular poly(alkylene sulphide)s as very useful catalysts. When used in conjunction with a Lewis acid such as aluminium or ferric chloride as an activator, and with sulphuryl chloride as the reagent, quantitative yields of chlorophenols can be obtained with very high regioselectivity in the presence of tiny amounts of the polymeric sulphides, usually in solvent-free conditions (unless the phenol starting material is solid at temperatures even above about 50 °C). Notably, poly(alkylene sulphide)s containing longer spacer groups are particularly para-selective in the chlorination of m-cresol and m-xylenol, while, ones with shorter spacers are particularly para-selective in the chlorination of phenol, 2-chlorophenol, and o-cresol. Such chlorination processes result in some of the highest para/ortho ratios reported for the chlorination of phenols. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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24 pages, 6726 KiB

Open AccessFeature PaperReview

A Review of the Synthetic Strategies toward Dihydropyrrolo[1,2-a]Pyrazinones

by Pieterjan Winant, Tomas Horsten, Shaiani Maria Gil de Melo, Flavio Emery and Wim Dehaen

Organics 2021, 2(2), 118-141; https://doi.org/10.3390/org2020011 - 4 Jun 2021

Cited by 7 | Viewed by 4979

Abstract

Dihydropyrrolo[1,2-a]pyrazinone rings are a class of heterocycles present in a wide range of bioactive natural products and analogues thereof. As a direct result of their bioactivity, the synthesis of this privileged class of compounds has been extensively studied. This review provides [...] Read more.

Dihydropyrrolo[1,2-a]pyrazinone rings are a class of heterocycles present in a wide range of bioactive natural products and analogues thereof. As a direct result of their bioactivity, the synthesis of this privileged class of compounds has been extensively studied. This review provides an overview of these synthetic pathways. The literature is covered up until 2020 and is organized according to the specific strategies used to construct the scaffold: fusing a pyrazinone to an existing pyrrole, employing a pyrazinone-first strategy, an array of multicomponent reactions and some miscellaneous reactions. Full article

(This article belongs to the Special Issue Feature Papers in Organics)

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