Benzoxazines applications

Very little is known about the parent benzoxazine analogue,1 due to difficulties in the preparation of o-nitrosophenol. Synthetic procedures and practical application of spironaphthooxazines can be found in the patent literature and have been reviewed.72... 

With the increasing demand for chiral nonracemic compounds, stereoselective methods for the synthesis of 1,3-oxazine derivatives and applications of enantiopure 1,3-oxazines in asymmetric transformations have gained in importance in the past decade, as reflected by the increasing trend in the number of publications on this topic, and accordingly by the share of this topic in the present compilation. The limited size of this survey and the scope of this chapter do not allow a discussion here of the applications of 1,3-oxazines in polymer chemistry and the synthesis and properties of 1,3-benzoxazine-containing hetero-calixarenes. 

While this chapter was being edited and revised, new data appeared on the chemistry of 1,3-oxazine derivatives. In a recent review on the applications of 1,3-amino alcohols in asymmetric organic syntheses, the use of numerous 1,3-oxazine derivatives for this purpose was discussed <2007CRV767>. A compilation on the progesterone receptor ligands provides a brief summary of the progesterone receptor modulatory effects of 6-aryl-l,4-dihydro-3,l-benzoxazin-2-ones <2007MI374>. 

The phytoalexins are a special class of defensive agents that has attracted much attention in view of agricultural applications. Perhaps the most advanced study concerns insecticidal and antimicrobial benzoxazins of the Gramineae, which have been elucidated to the gene level (Frey 1997). A survey of phytoalexins is presented in Chart 12.2. 

Benzoxazin-4-ones have been known for many years and are made by the cyclization of O-benzoylsalicylamides or reactions between phenyl salicylates and benzamidines (l5LA(409)305>. The first of these two methods obviously has wide applicability and when 2-acyl-mercaptobenzamides are used l,3-benzothiazin-4-ones are obtained (Scheme 77) (67BSF4441). 

Colorless derivatives of the carbinol bases of cationic dyes have recently found application for the manufacture of carbonless copy paper and for special paper used for thermal printers. Examples of such color formers are the crystal violet derivative 31 [29], which develops a blue color, and the black-developing fluorane lactone 32 [30] and benzoxazine 33 [31],... 

APCI has become a popular ionization source for applications of coupled HPLC-MS. Figure 1.33 shows an example of an application of HPLC-APCI coupling [79]. It shows the analysis obtained from extracts of maize plants. Six compounds are identified by mass spectrometry. These compounds have been identified as glucoconjugated DIMBOA (2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one) and similar molecules that differ by the number of methoxy groups in the benzene ring and/or by the N-O methylation of the hydroxamate function. This example clearly shows the influence of the analyte on the type of observed molecular species. Indeed, the presence of an acidic group in the compound from peak 1 allows mainly the detection of deprotonated molecular ions, whereas the compound from peak 4 does not contain an acid group and thus leads only to the formation of adduct ions. 

Potassium organophosphide reagents also continue to find applications in synthesis. Direct displacement of fluoride from fluoroaromatic substrates by potassium diphenylphosphide is the key step in the synthesis of the phosphi-noarylsulfoxides (88), water-soluble phosphino-amino acid systems, e.g. (89), ° and the chiral benzoxazine system (90). Related displacement of fluoride by potassium monophenylphosphide has been used to prepare a series of hydrophilic triarylphosphines, e.g. (91). Among new phosphines prepared by conventional displacement reactions by potassium diphenylphosphide on... 

Other thermosetting polymers are cyanate esters (CEs), benzoxazines, PU acrylates, bismaleimides (BMIs), dicy-clopentadienes (DCPDs), diallyl phthalates (DAPs), etc. Formulations based on these polymers are used for specific applications where their particular properties are required. For example, DAP has long been the material of choice for electrical components where long-term reliability is required. 

The transition metal-catalyzed reductive carbonylation of o-substituted nitrobenzenes is a useful method for the synthesis of nitrogen heterocycles. Application of this methodology to the preparation of l,4-dihydro-2/f-3,l-benzoxazin-2-one derivatives and to the synthesis of the 3,1-benzox-azepin-2-one (42) has been reported <93JOM(451)157>. Reaction of 2-(2-nitrophenyl)ethanol (41) (100% conversion) with carbon monoxide in the presence of a palladium(Il) catalyst gave (42) in 60% yield, together with some of the macrocyclic dimer (43) ( nation (2)). It is suggested that a nitrene complex may not be involved with the palladium catalyst in view of the reaction path selectivity observed <93JOM(45i)l57>. 

Easy and efficient access routes to heterocyclic complexes are of significant interest in organic chemistry and its application in synthesis both in the laboratory and industry. During the recent years several novel routes toward such compounds in aqueous media have been described. 2-Substituted 3,4-dihydro-2H-l,4-benzoxazines have been prepared in excellent yields and short reaction times through the cyclization of hydroxysulfonamides in water under phase-transfer catalysis conditions (Scheme 3) [25]. 

Coordination polymers containing rotaxane linkers 12CSR5896. Design and synthesis of cross-Hnked poly(benzoxazine)- and polybenzimidazole-based copolymer membranes and their application to an electrolyte membrane for a high-temperature PEM fuel cell 13P77. 

Schreiber, for the preparation of phenolic resins with improved thermal, mechanical, and dielectric characteristics. However, no systematic study was reported in Schreiber s patents. Thus, it was of interest to examine in more detail several points such as 1) the synthesis of an homologeous series of benzoxazines, 2) their reaction with phenols, which may be considered as the initiation step of the polymerization by a ring opening mechanism, 3) the pol3nnerization kinetics of benzoxazines, initiated either thermally or with phenols, and 4) the application possibilities of these monomers and polymers. 

Rao B S and Palanisamy A (2011), Monofunctional benzoxazine from cardanol for biocomposite applications . React Fund Polym, 71, 148-154, and references therein. 

Other examples of flame retardant applications include incorporation of N3P3CI6 in a fiber-reinforced poly(benzoxazine-co-E-caprolactam) and modified cyclophosphazenes containing a phosphaphenanthrene end groups. ... 

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