Synthesis Of Benzoxazines Research Articles

Synthesis of Renewable Furan-Based Benzoxazines and Polybenzoxazines: Recent Advances.

The burgeoning field of materials science is currently witnessing a paradigm shift toward the utilization of renewable plant biomass as a viable chemical source for the production of sustainable materials. This trend is substantiated by a significant corpus of recent experimental and theoretical research focused on the synthesis and property analysis of such polymers. Within this context, polybenzoxazines stand out as a pioneering class of thermosetting polymers, distinguished by their exceptional thermal and mechanical characteristics, coupled with the feasibility of synthesizing their precursor monomers from eco-friendly, renewable resources, including plant phenols and furfurylamine. Opting for furfurylamine over traditional aniline and its petroleum-derived counterparts in the synthesis of benzoxazines not only increases the eco-compatibility of the resultant materials but also imparts a significant alteration to their properties. This short review, spanning the last three years, delves into the principal advancements achieved in the realm of novel furan-bearing benzoxazines and polybenzoxazines from 2021 to present, accentuating both the triumphs and challenges encountered in this burgeoning domain.

Protonation Effects on the Benzoxazine Formation Pathways and Products Distribution.

The effect of acidic media on the formation of the 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine Bz is evaluated, focusing on the differentiation of intermediates and products formed by the distinct pathways observed in the presence and absence of acid. The use of real-time mass spectrometry (PSI-ESI-MS) coupled to tandem mass spectrometry and infrared multiple photon dissociation (IRMPD) allowed the differentiation of the species observed during the synthesis of benzoxazines in these different conditions. The results suggest that formic acid promotes the formation of aniline and phenol condensation products (IC and IIC) by protecting the aniline amino group and enhancing the formaldehyde electrophilicity. The results also suggest that although the presence of acid allow a more efficient potential energy landscape to be accessed, the last cyclization step for the formation of benzoxazines cannot be mediated by the protonation route intermediate (ROP Bz). Overall, the conclusions presented here provide important information about the synthesis of benzoxazines under acidic conditions, allowing the development of optimal reaction conditions.

Synthesis of Benzoxazines by Heterogeneous Multicomponent Biochemo Multienzymes Cascade Reaction.

This work describes the possibility to combine multicomponent chemistry and multienzymes cascade transformations in a unique reactive framework to yield highly functionalized 1,4-benzoxazines under favorable heterogeneous conditions. The synthetic scheme involved the generation in situ of electrophilic reactive quinone intermediates of tyrosol esters catalyzed by lipase M and tyrosinase followed by nucleophilic 1,6-Michael addition of selected α-amino acid methyl esters, and successive intramolecular lactonization and aromatization processes. The immobilization of the multienzymes cascade on electroactive lignin nanoparticles improved the sustainability and recyclability of the overall system.

Electrochemical oxidative cyclization of N-allylamides for the synthesis of CF3-containing benzoxazines and oxazolines.

The introduction of trifluoromethyl (-CF3) groups into compounds is a common synthetic strategy in organic chemistry. Commonly used methods for introducing trifluoromethyl groups are limited by harsh reaction conditions, low regioselectivity, or the need for excess reagents. In this study, a facile electrochemical oxidative and radical cascade cyclization of N-(2-vinylphenyl)amides for the synthesis of CF3-containing benzoxazines and oxazolines was obtained. This sustainable protocol features inexpensive and durable electrodes, a wide range of substrates, diverse functional group compatibility under transition-metal-free, external-oxidant-free, and additive-free conditions, and can be applied in an open environment.

Photoelectrochemical synthesis of 4-halomethyl benzoxazines with a halogen anion source

A mild and efficient protocol for preparing 4-halomethyl benzoxazines via a photoelectrochemical process with ammonium halide as the halogenating reagent was developed.

Synthesis, Computational Studies, and Anti-Tuberculosis Activity of Benzoxazines That Act as RAGE Inhibitors

Novel benzoxazines were synthesized by microwave irradiation and tested for their potential binding affinity towards receptors of advanced glycation end products (RAGE). We found that the compound (2-(2-bromophenyl)-6-methyl-2,4-dihydro-1H-benzo[d][1,3]oxazine) (3i) is a lead inhibitor of RAGE. Further, our in silico prediction that benzoxazines dock towards the AGE binding region of RAGE suggests that these ligands could bind effectively at the hydrophobic pocket of the receptor and additionally form key interactions with Arg48 and Arg104, revealing its diversity in developing anti-RAGE drugs to treat AGE–RAGE-dominant disease conditions. Functionally, we herein report the anti-tuberculosis activity of small molecules which could be bioactive in the culture of mycobacterium tuberculosis.

Visible-light-promoted tandem radical difunctionalization of olefinic amides: a direct access to NO2-containing benzoxazines and oxazolines

A visible-light assisted cascade radical nitration/cyclization has been reported for the synthesis of nitrated benzoxazines and oxazolines using olefinic amides and N-nitrosuccinimide as precursors.

Intermolecular hydrogen bonding effects on the reaction of dianisidine, bisphenol A (BPA) and formaldehyde

The synthesis of benzoxazines is a fundamental step in obtaining polybenzoxazine resins, understanding its formation mechanism is important to improve the properties of these resins. This paper analyses the Mannich-type reaction between o-dianisidine, bisphenol A (BPA) and formaldehyde. Spectroscopic studies and computational calculations revealed that this reaction only produced a monobenzoxazine, resulting from the formation of cyclic arrays by intermolecular hydrogen bonds between o-dianisidine and BPA. Such cyclic arrays prevented bifunctional benzoxazine and/or oligomer formation.

One Pot Synthesis of Benzopyranones and Benzoxazinones Catalyzed by MMO

One pot synthesis of benzopyranones and benzoxazinones is aimed to develop an environment friendly strategy in which the requisite moiety is constructed by using functionality of chalcones and mixed metal oxides (MMO). MMO, as catalyst are the topic of continuing interest due to their versatile applications in the field of organic synthesis. A novel approach to the synthesis of benzopyranones and benzoxazines with high pharmaceutical activity is sought to eliminate the use of volatile organic solvents. A new methodology is designed to carry out the synthesis in a single step with enhance reaction rate with high yield.

One‐Pot Divergent Synthesis of Benzoxazines and Dihydroquinolines from Morita‐Baylis‐Hillman Alcohols

AbstractBenzoxazines and hydroquinolines have been prepared by a one‐pot process via catalyst‐controlled divergent annulations of Morita‐Baylis‐Hillman (MBH) alcohols. In the presence of diazabicyclo[2.2.2]octane, MBH alcohols reacted with Boc2O to form MBH carbonates, followed by intramolecular annulation to give 4H‐benzo[d][1,3]oxazines. Divergently, the combination of Bu4NBr and NaOH enabled the formation of 1,2‐dihydroquinolines from the same starting materials.

Synthesis, ring-opening polymerization, and properties of benzoxazines based on o- and p-hydroxybenzyl alcohols

Two series of bifunctional benzoxazines were synthesized from o- and p-hydroxybenzyl alcohols ( oHBA and pHBA), three aliphatic diamines containing ether linkage (Jeffamines D230 and D400 and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA)), and paraformaldehyde. The chemical structures of the benzoxazines were confirmed by 1H and 13C nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. The ring-opening polymerization of the benzoxazines was studied by differential scanning calorimetry and FTIR, respectively. oHBA-based benzoxazines respectively exhibit lower onset temperatures of ring-opening polymerization than pHBA-based counterparts due to the O–H∙∙∙O intramolecular hydrogen-bonding interaction between the hydrogen of ortho-methylol group and the oxygen in oxazine ring, and oHBA-based polybenzoxazines respectively show lower glass transition temperatures ( Tgs) than pHBA-based counterparts due to the difference in crosslinking density caused by the steric hindrance effect of the position of methylol group on the polymerization of benzoxazine monomers. In each of the two series of benzoxazines, the onset temperature of ring-opening polymerization of D230-based benzoxazine is close to that of TTDDA-based analogue and lower than that of D400-based counterpart owing to the steric effect of the chain length and chain volume of the bridging structure between the oxazine rings on the polymerization, and the Tg of D230-based polybenzoxazine is close to that of TTDDA-based analogue and much higher than that of D400-based counterpart owing to the difference in crosslinking density caused by the steric hindrance effect of the bridging structure on the polymerization of benzoxazine monomers. In addition, all the polybenzoxazines exhibit thermally induced shape memory effect. In each of the two series of polybenzoxazines, the shape recovery rate and ratio of D400-based polybenzoxazine are respectively close to those of D230-based counterpart and higher than those of TTDDA-based analogue due to the difference in network architecture.

Synthesis and Characterization of Polyetheramine-type Benzoxazines as Protective Coatings for Low Carbon Steel against Corrosion in Sodium Chloride Solution

Synthesis and Characterization of Polyetheramine-type Benzoxazines as Protective Coatings for Low Carbon Steel against Corrosion in Sodium Chloride Solution

Recent Advances in Flame Retardant Bio-Based Benzoxazine Resins

Benzoxazines have attracted wide attention from academics all over the world because of their unique properties. However, most of the production and preparation of benzoxazine resins depends on petroleum resources now, especially bisphenol A-based benzoxazine. Therefore, owing to the environmental impacts, the development of bio-based benzoxazines is gaining more and more interest to substitute petroleum-based benzoxazines. Similar to petroleum-based benzoxazines, most of bio-based benzoxazines suffer from flammability. Thus, it is necessary to endow bio-based benzoxazines with outstanding flame retardancy. The purpose of this review is to summarize the latest advance in flame retardant bio-based benzoxazines. First, three methods of the synthesis of bio-based benzoxazines are introduced briefly. Furthermore, the curing mechanism of benzoxazine and the effect of branched chains on the curing behavior are also discussed and summarized. Subsequently, this review focuses on fully bio-based benzoxazines, partly bio-based benzoxazines, and bio-based benzoxazine composite materials in terms of flame retardancy as well as thermal stability and some other special properties. Finally, we give a brief comment on the challenges and prospects of the future development of flame retardant bio-based benzoxazines.

Iodine-mediated oxythiolation of o-vinylanilides with disulfides for the synthesis of benzoxazines.

An efficient iodine-mediated oxythiolation of o-vinylanilides with disulfides was developed. By virtue of this method, a series of thio-tethered benzoxazine derivatives were synthesized in good to excellent yields. The reaction features high yields, is metal-free, and has a wide substrate scope.

KINETIC MODELING OF MAIN-CHAIN BENZOXAZINE POLYMER SYNTHESIS STUDIED USING POLYMATH: CASE STUDY

This study reports kinetics of benzoxazine synthesis of main chain type benzoxazine polymer (MCBP(BA-a)), which was derived using Mannich condensation reaction of bisphenol-A with formaldehyde and aniline. The chemical structural of MCBP(BA-a) was confirmed by Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). Kinetics of benzoxazine (BZ) synthesis was theoretically studied using Polymath Software. The synthesis of BZ precursors consist of two main reactions. Reaction of amine with formaldehyde, and then followed by the reaction of phenolic compound with the intermediate component of the first reaction. Therefore, the effect of the reaction constant ratio (

N‐alkyl imidazole‐based homonuclear coordination complex as a neutral organocatalyst for the faster and efficient construction of 3,4‐dihydro‐2H‐1,3‐oxazine scaffold

AbstractIn the present work, homonuclear coordination complex including Zn (II) andN‐hexadecylimidazole ligand was used for the first time as a highly efficient homogeneous neutral organocatalyst for the synthesis of 3,4‐dihydro‐2H‐1,3‐benzoxazine monomers. Therefore,N‐alkyl orN‐aryl substituted, both mono‐benzoxazine and bis‐benzoxazine, were successfully synthesized (21 examples) via Mannich‐type condensation reactions. Effortlessly obtaining the pure product with high yields and the short reaction time makes this method more useful and advantageous than the common existing benzoxazine synthesis methods.

Synthesis and properties of the bio-based isomeric benzoxazine resins: Revealing the effect of the neglected short alkyl substituents

Bio-based feedstocks usually contain many isomers with similar structures, and the short alkyl substituents are generally considered as low-reactive groups in benzoxazine chemistry due to their low induction effect and chemical inertness. Therefore, little attention has been paid on their effects on the synthesis or properties of benzoxazine. In this work, two bio-based benzoxazine isomers (CAR-fbz and THY-fbz) containing methyl and isopropyl groups with interchanged positions were synthesized from the renewable carvacrol and thymol. Their synthetic process, crystal features, and curing reactions were carefully investigated. Results showed that different side reacitions and by-products were detected under the same synthese conditions. And using the similar purification method, CAR-fbz and THY-fbz with high purity were found to have different crystal features. In addition, the cured systems also indicated varied H-bonding features and thermal properties based on differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) results. With the help of density functional theory (DFT) calculation, the reasons were attributed to the different electrophilicity of phenol moiety, varied molecular symmetry and intermolecular interaction caused by the overlooked short alkyls. Summarily, the leverage of short-chain alkyl groups on benzoxazine chemistry is revealed. The result is significant for the benzoxazine synthesis, especially when the renewable compounds are taken as the starting materials for bio-based benzoxazine preparation, which often has many isomers with similar structures.

New opportunity for sustainable benzoxazine synthesis: A straight and convenient one-pot protocol for formaldehyde-free bio-based polymers

Polybenzoxazine is an interesting class of high-performance polymers with potential applications in both the scientific and industrial fields. Due to its remarkable properties along with environmental concerns, different benzoxazine monomers are being synthesized in order to afford more sustainable alternatives for polymeric materials development. Here, we report a microwave-assisted and formaldehyde-free methodology for the synthesis of a cardanol-based benzoxazine. The reaction use cardanol and HMTA as starting materials with the efficient microwave-assisted heating, affording the desired product in a matter of minutes and high yields, in a reaction system completely absent of organic solvents. Monomer characterization was performed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance Spectroscopy (1H and 13C NMR) and differential scanning calorimetry (DSC). The obtained thermoset was studied by thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), showing good thermal and mechanical properties. The results indicate the successful protocol for the development of highly bio-based monomer under solvent- and formaldehyde-free conditions, starting form cardanol, an agro-industrial residue.

Synthesis of Novel Benzoxazines Containing Sulfur and Their Application in Rubber Compounds.

This work reports the synthesis and successful use of novel benzoxazines as reinforcing resins in polyisoprene rubber compounds. For this purpose, three new dibenzoxazines containing one (4DTP-fa) or two heteroatoms of sulfur (3DPDS-fa and 4DPDS-fa) were synthesized following a Mannich condensation reaction. The structural features of each benzoxazine precursor were characterized by 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and Raman. The new precursors showed well suited reactivity as characterized by differential scanning calorimetry (DSC) and rheology and were incorporated in rubber compounds. After the mixing, the curing profiles, morphologies and mechanical properties of the materials were tested. These results show that the structural feature of each isomer was significantly affecting its behavior during the curing of the rubber compounds. Among the tested benzoxazines, 3DPDS-fa exhibited the best ability to reinforce the rubber compound even compared to common phenolic resin. These results prove the feasibility to reinforce rubber compounds with benzoxazine resins as a possible alternative to replace conventional phenolic resins. This paper provides the first guide to use benzoxazines as reinforcing resins for rubber applications, based on their curing kinetics.

Electrochemical oxidative radical cascade cyclization of olefinic amides and thiophenols towards the synthesis of sulfurated benzoxazines, oxazolines and iminoisobenzofurans

Heterocycles containing N and O are important structures in pharmaceuticals, agrochemicals and functional molecules.