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12 pages, 1260 KiB

Open AccessArticle

One-Pot Synthesis of 1,3,4-Oxadiazines from Acylhydrazides and Allenoates

by Su Been Kim, Santanu Maiti, Eun Sun Park, Ga Young Kim, Yunji Choun, Soon Kil Ahn, Jae Kwang Kim and Jinho Kim

Molecules 2023, 28(9), 3815; https://doi.org/10.3390/molecules28093815 - 29 Apr 2023

Cited by 1 | Viewed by 1652

Abstract

The framework of 1,3,4-oxadiazine is crucial for numerous bioactive molecules, but only a limited number of synthetic methods have been reported for its production. In 2015, Wang’s group developed a 4-(dimethylamino)pyridine (DMAP)-catalyzed [2 + 4] cycloaddition of allenoates with N-acyldiazenes, which provided [...] Read more.

The framework of 1,3,4-oxadiazine is crucial for numerous bioactive molecules, but only a limited number of synthetic methods have been reported for its production. In 2015, Wang’s group developed a 4-(dimethylamino)pyridine (DMAP)-catalyzed [2 + 4] cycloaddition of allenoates with N-acyldiazenes, which provided an atom-efficient route for 1,3,4-oxadiazines. However, the practicality of this method was limited by the instability of N-acyldiazenes as starting materials. Building upon our ongoing research about the aerobic oxidation of hydrazides and their synthetic applications, we hypothesized that aerobic oxidative cycloadditions using acylhydrazides instead of N-acyldiazenes may provide a more practical synthetic route for 1,3,4-oxadiazines. In this manuscript, we describe a one-pot synthetic protocol for 1,3,4-oxadiazines from acylhydrazides and allenoates. The developed one-pot protocol consists of aerobic oxidations of acylhydrazides into N-acyldiazenes using NaNO₂ and HNO₃, followed by the DMAP-catalyzed cycloaddition of allenoate with the generated N-acyldiazenes. A variety of 1,3,4-oxadiazines were produced in good to high yields. In addition, the practicality of the developed method was demonstrated by a gram-scale synthesis of 1,3,4-oxadiazine. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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15 pages, 3928 KiB

Open AccessArticle

Synthesis and Properties of 1,3-Disubstituted Ureas Containing (Adamantan-1-yl)(phenyl)methyl Fragment Based on One-Pot Direct Adamantane Moiety Inclusion

by Vladimir D’yachenko, Dmitry Danilov, Yaroslav Kuznetsov, Semyon Moiseev, Vladimir Mokhov, Vladimir Burmistrov and Gennady Butov

Molecules 2023, 28(8), 3577; https://doi.org/10.3390/molecules28083577 - 19 Apr 2023

Cited by 1 | Viewed by 1242

Abstract

A one-stage method for the preparation of 1-[isocyanato(phenyl)methyl]adamantane containing a phenylmethylene fragment located between the adamantane fragment and the isocyanate group, and 1-[isocyanato(phenyl)methyl]-3,5-dimethyladamantane with additional methyl groups at the nodal positions of adamantane, with a yield of 95% and 89%, respectively, is described. [...] Read more.

A one-stage method for the preparation of 1-[isocyanato(phenyl)methyl]adamantane containing a phenylmethylene fragment located between the adamantane fragment and the isocyanate group, and 1-[isocyanato(phenyl)methyl]-3,5-dimethyladamantane with additional methyl groups at the nodal positions of adamantane, with a yield of 95% and 89%, respectively, is described. The method includes the direct inclusion of an adamantane moiety through the reaction of phenylacetic acid ethyl ester with 1,3-dehydroadamantane or 3,5-dimethyl-1,3-dehydroadamantane followed by the hydrolysis of the obtained esters. The reaction of 1-[isocyanato(phenyl)methyl]adamantane with fluorine(chlorine)-containing anilines gave a series of 1,3-disubstituted ureas with 25–85% yield. 1-[Isocyanato(phenyl)methyl]-3,5-dimethyladamantane was involved in the reactions with fluorine(chlorine)-containing anilines and trans-4-amino-(cyclohexyloxy)benzoic acid to obtain another series of ureas with a yield of 29–74%. The resulting 1,3-disubstituted ureas are promising inhibitors of the human soluble epoxide hydrolase (hsEH). Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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14 pages, 3391 KiB

Open AccessArticle

Diastereoselective Synthesis of cis-2,6-Disubstituted Dihydropyrane Derivatives through a Competitive Silyl-Prins Cyclization versus Alternative Reaction Pathways

by Laura F. Peña, Enol López, Ángel Sánchez-González and Asunción Barbero

Molecules 2023, 28(7), 3080; https://doi.org/10.3390/molecules28073080 - 30 Mar 2023

Cited by 2 | Viewed by 1463

Abstract

A convenient regioselective synthesis of allyl- and vinylsilyl alcohols, from a common precursor, was described, by selecting the appropriate reaction conditions. Allyl- and vinylsilyl alcohols were tested in silyl-Prins cyclizations for the preparation of disubstituted oxygenated heterocycles in a one-pot sequential reaction. The [...] Read more.

A convenient regioselective synthesis of allyl- and vinylsilyl alcohols, from a common precursor, was described, by selecting the appropriate reaction conditions. Allyl- and vinylsilyl alcohols were tested in silyl-Prins cyclizations for the preparation of disubstituted oxygenated heterocycles in a one-pot sequential reaction. The methodology was sensitive to the structure of the starting alkenylsilyl alcohol and reaction conditions, with competitive pathways observed (particularly for allylsilyl alcohols), such as Peterson elimination and oxonia-Cope reactions. However, the use of vinylsilyl alcohols allowed the preparation of differently disubstituted cis-2,6-dihydropyrans in moderate to good yields. Computational studies support the proposed mechanism. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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12 pages, 1915 KiB

Open AccessArticle

One-Pot Solvent-Involved Synthesis of 5-O-Substituted 5H-Chromeno[2,3-b]pyridines

by Yuliya E. Ryzhkova, Fedor V. Ryzhkov, Michail N. Elinson, Oleg I. Maslov and Artem N. Fakhrutdinov

Molecules 2023, 28(1), 64; https://doi.org/10.3390/molecules28010064 - 21 Dec 2022

Cited by 2 | Viewed by 1337

Abstract

Chromeno[2,3-b]pyridines are substances demanded in medicinal and material chemistry. PASE (pot, atom, and step economy) and in particular one-pot approaches are key green chemistry techniques that are applied for the synthesis of heterocyclic compounds. In this case, the PASE approach was [...] Read more.

Chromeno[2,3-b]pyridines are substances demanded in medicinal and material chemistry. PASE (pot, atom, and step economy) and in particular one-pot approaches are key green chemistry techniques that are applied for the synthesis of heterocyclic compounds. In this case, the PASE approach was extended with ‘component economy’, as solvent was used also as reactant (solvent-involved reaction). This approach was adopted for the one-pot synthesis of previously unknown O-substituted 5-alkoxy-5H-chromeno[2,3-b]pyridines via two-step transformation, namely the reaction of salicylaldehydes and malononitrile dimer, with the subsequent addition of alcohol. The mechanistic studies revealed the possibility of concurrent reaction. The studies aided in optimizing the reaction conditions for the best yields (77–93%). Thus, the one-pot reaction proceeds efficient and quickly, and the work-up procedure (only simple filtering) is very convenient. The structure of synthesized chromeno[2,3-b]pyridines was confirmed by 2D NMR spectroscopy. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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16 pages, 32409 KiB

Open AccessArticle

Catalytic Performance of Immobilized Sulfuric Acid on Silica Gel for N-Formylation of Amines with Triethyl Orthoformate

by Sodeeq Aderotimi Salami, Xavier Siwe-Noundou and Rui W. M. Krause

Molecules 2022, 27(13), 4213; https://doi.org/10.3390/molecules27134213 - 30 Jun 2022

Cited by 6 | Viewed by 1944

Abstract

In the search for convenient, green, and practical catalytic methods for the current interest in organic synthesis, a simple, green, and highly efficient protocol for N-formylation of various amines was carried out in the presence of immobilized sulfuric acid on silica gel [...] Read more.

In the search for convenient, green, and practical catalytic methods for the current interest in organic synthesis, a simple, green, and highly efficient protocol for N-formylation of various amines was carried out in the presence of immobilized sulfuric acid on silica gel (H₂SO₄–SiO₂). All reactions were performed in refluxing triethyl orthoformate (65 °C). The product formamides were obtained with high-to-excellent yields within 4 min to 2 h. The current approach is advantageous, due to its short reaction time and high yields. The catalyst is recyclable with no significant loss in catalytic efficiency. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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10 pages, 24352 KiB

Open AccessArticle

Co-N-Si/AC Catalyst for Aerobic Oxidation of Benzyl Alcohols to Esters under Mild Conditions

by Changjian Zhou, Rong Sun, Yuting Zhang, Biao Xiong, Hui Dai and Yong Dai

Molecules 2021, 26(22), 6792; https://doi.org/10.3390/molecules26226792 - 10 Nov 2021

Cited by 1 | Viewed by 1582

Abstract

A stable, earth-abundant, reusable cobalt-based heterogeneous catalyst is developed for the oxidative esterification of alcohols under ambient conditions, featuring broad substrate scope, providing good to excellent product yields. This protocol enables easy recyclability of the catalyst, measured up to five times without significant [...] Read more.

A stable, earth-abundant, reusable cobalt-based heterogeneous catalyst is developed for the oxidative esterification of alcohols under ambient conditions, featuring broad substrate scope, providing good to excellent product yields. This protocol enables easy recyclability of the catalyst, measured up to five times without significant loss of efficiency. The active sites of Co-N-Si/AC are proposed to be Co-N species. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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9 pages, 2769 KiB

Open AccessCommunication

Photoinduced Atom Transfer Radical Addition/Cyclization Reaction between Alkynes or Alkenes with Unsaturated α-Halogenated Carbonyls

by Kazuki Matsuo, Tadashi Yoshitake, Eiji Yamaguchi and Akichika Itoh

Molecules 2021, 26(22), 6781; https://doi.org/10.3390/molecules26226781 - 10 Nov 2021

Cited by 8 | Viewed by 2833

Abstract

We have developed a photochemical ATRA/ATRC reaction that is mediated by halogen bonding interactions. This reaction is caused by the reaction of malonic acid ester derivatives containing bromine or iodine with unsaturated compounds such as alkenes and alkynes in the presence of diisopropylethylamine [...] Read more.

We have developed a photochemical ATRA/ATRC reaction that is mediated by halogen bonding interactions. This reaction is caused by the reaction of malonic acid ester derivatives containing bromine or iodine with unsaturated compounds such as alkenes and alkynes in the presence of diisopropylethylamine under visible light irradiation. As a result of various control experiments, it was found that the formation of complexes between amines and halogens by halogen-bonding interaction occurs in the reaction system, followed by the cleavage of the carbon–halogen bonds by visible light, resulting in the formation of carbon radicals. In this reaction, a variety of substrates can be used, and the products, cyclopentenes and cyclopentanes, were obtained by intermolecular addition and intramolecular cyclization. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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8 pages, 3858 KiB

Open AccessArticle

Greener Synthesis of Pristane by Flow Dehydrative Hydrogenation of Allylic Alcohol Using a Packed-Bed Reactor Charged by Pd/C as a Single Catalyst

by Takayoshi Kasakado, Yuki Hirobe, Akihiro Furuta, Mamoru Hyodo, Takahide Fukuyama and Ilhyong Ryu

Molecules 2021, 26(19), 5845; https://doi.org/10.3390/molecules26195845 - 27 Sep 2021

Cited by 1 | Viewed by 2045

Abstract

Our previous work established a continuous-flow synthesis of pristane, which is a saturated branched alkane obtained from a Basking Shark. The dehydration of an allylic alcohol that is the key to a tetraene was carried out using a packed-bed reactor charged by an [...] Read more.

Our previous work established a continuous-flow synthesis of pristane, which is a saturated branched alkane obtained from a Basking Shark. The dehydration of an allylic alcohol that is the key to a tetraene was carried out using a packed-bed reactor charged by an acid–silica catalyst (HO-SAS) and flow hydrogenation using molecular hydrogen via a Pd/C catalyst followed. The present work relies on the additional propensity of Pd/C to serve as an acid catalyst, which allows us to perform a flow synthesis of pristane from the aforementioned key allylic alcohol in the presence of molecular hydrogen using Pd/C as a single catalyst, which is applied to both dehydration and hydrogenation. The present one-column-two-reaction-flow system could eliminate the use of an acid catalyst such as HO-SAS and lead to a significant simplification of the production process. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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Review

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25 pages, 11364 KiB

Open AccessReview

Engaging Isatins and Amino Acids in Multicomponent One-Pot 1,3-Dipolar Cycloaddition Reactions—Easy Access to Structural Diversity

by Hua Zhao and Yufen Zhao

Molecules 2023, 28(18), 6488; https://doi.org/10.3390/molecules28186488 - 07 Sep 2023

Cited by 2 | Viewed by 1117

Abstract

Multicomponent reactions (MCRs) have undoubtedly emerged as the most indispensable tool for organic chemists worldwide, finding extensive utility in the synthesis of intricate natural products, heterocyclic molecules with significant bioactivity, and pharmaceutical agents. The multicomponent one-pot 1,3-dipolar cycloaddition reactions, which were initially conceptualized [...] Read more.

Multicomponent reactions (MCRs) have undoubtedly emerged as the most indispensable tool for organic chemists worldwide, finding extensive utility in the synthesis of intricate natural products, heterocyclic molecules with significant bioactivity, and pharmaceutical agents. The multicomponent one-pot 1,3-dipolar cycloaddition reactions, which were initially conceptualized by Rolf Huisgen in 1960, find extensive application in contemporary heterocyclic chemistry. In terms of green synthesis, the multicomponent 1,3-dipolar cycloaddition is highly favored owing to its numerous advantages, including high step- and atom-economies, remarkable product diversity, as well as excellent efficiency and diastereoselectivity. Among the numerous pieces of research, the most fascinating reaction involves the utilization of azomethine ylides generated from isatins and amino acids that can be captured by various dipolarophiles. This approach offers a highly efficient and convenient method for constructing spiro-pyrrolidine oxindole scaffolds, which are crucial building blocks in biologically active molecules. Consequently, this review delves deeper into the dipolarophiles utilized in the 1,3-dipolar cycloaddition of isatins and amino acids over the past six years. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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17 pages, 4717 KiB

Open AccessFeature PaperReview

Ugi Four-Component Reactions Using Alternative Reactants

by Seyyed Emad Hooshmand and Wei Zhang

Molecules 2023, 28(4), 1642; https://doi.org/10.3390/molecules28041642 - 08 Feb 2023

Cited by 5 | Viewed by 4990

Abstract

The Ugi four-component reaction (Ugi-4CR) undoubtedly is the most prominent multicomponent reaction (MCRs) that has sparked organic chemists’ interest in the field. It has been widely used in the synthesis of diverse heterocycle molecules such as potential drugs, natural product analogs, pseudo peptides, [...] Read more.

The Ugi four-component reaction (Ugi-4CR) undoubtedly is the most prominent multicomponent reaction (MCRs) that has sparked organic chemists’ interest in the field. It has been widely used in the synthesis of diverse heterocycle molecules such as potential drugs, natural product analogs, pseudo peptides, macrocycles, and functional materials. The Ugi-4CRs involve the use of an amine, an aldehyde or ketone, an isocyanide, and a carboxylic acid to produce an α-acetamido carboxamide derivative, which has significantly advanced the field of isocyanide-based MCRs. The so-called intermediate nitrilium ion could be trapped by a nucleophile such as azide, N-hydroxyphthalimide, thiol, saccharin, phenol, water, and hydrogen sulfide instead of the original carboxylic acid to allow for a wide variety of Ugi-type reactions to occur.β In addition to isocyanide, there are alternative reagents for the other three components: amine, isocyanide, and aldehyde or ketone. All these alternative components render the Ugi reaction an aptly diversity-oriented synthesis of a myriad of biologically active molecules and complex scaffolds. Consequently, this review will delve deeper into alternative components used in the Ugi MCRs, particularly over the past ten years. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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39 pages, 9838 KiB

Open AccessReview

Recent Developments on Five-Component Reactions

by Xiaoming Ma, Sanjun Zhi and Wei Zhang

Molecules 2021, 26(7), 1986; https://doi.org/10.3390/molecules26071986 - 01 Apr 2021

Cited by 18 | Viewed by 2641

Abstract

Multicomponent reactions (MCRs) have inherent advantages in pot, atom, and step economy (PASE). This important green synthetic approach has gained increasing attention due to high efficiency, minimal waste, saving resources, and straightforward procedures. Presented in this review article are the recent development on [...] Read more.

Multicomponent reactions (MCRs) have inherent advantages in pot, atom, and step economy (PASE). This important green synthetic approach has gained increasing attention due to high efficiency, minimal waste, saving resources, and straightforward procedures. Presented in this review article are the recent development on 5-compoment reactions (5CRs) of the following six types: (I) five different molecules A + B + C + D + E; pseudo-5CRs including (II) 2A + B + C + D, (III) 2A + 2B + C, (IV) 3A + B + C, (V) 3A + 2B, and (VI) 4A + B. 5CRs with more than five-reaction centers are also included. Full article

(This article belongs to the Special Issue Green and Highly Efficient One-Pot Synthesis and Catalysis)

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