Benzoxazines characteristics

The linear regression analysis data are listed in Table VIII. For ease of comparison, the data on the parent 2-aryltetrahydro-l,3-oxazine 389 and the corresponding 1,3- and 3,1-benzoxazine isomers 392 and 397 are also given. The data in Table VIII show that p is practically the same for all the 1,3-oxazine ring systems investigated, whereas the intercept values are characteristic of the substituents. 

H and NMR studies on 477-3,l-benzoxazin-4-one derivatives 12 and their acylanthranilic acid precursors 13 led to the conclusion that differentiation between these two series of compounds was best achieved through the characteristic coupling interactions in the high-frequency carbonyl region <2000SAA1079>. 

The effects of stereochemistry, substitution, and (for 2-phenylimino derivatives) an intramolecular cyclization of the ions [M-H] have been observed in the electron ionization mass spectra of as- and /ra r-fused 4-phenyloctahy-dro-2//-3,l-benzoxazin-2-ones 21 and -2-thiones 22, 2,4-diphenylhexahydro-3,l-benzoxazines 23, and 2-phenyl-imino-4-phenylhexahydro-3,l-benzoxazines 24. The mass spectral behavior was similar for the isomeric compounds, although they could usually be differentiated from each other on the basis of the relative abundances of their characteristic fragment ions <2005ARK(iv)39>. 

Nitroalkenes react with benzene derivatives at low temperature in triflic acid to afford a-aryl ketones after quenching with methanol182,183 [Eq. (5.74)]. At higher temperature the 0-protonated oxime intermediate may react further to yield 4//-1,2-benzoxazines (see Section 5.14.1.3). a-Nitrocarbonyl compounds show similar characteristics as alkylating agents to yield oximes with the involvement of the tricationic intermediate 44.181... 

P. Tardieu, R. Dubest, J. Aubard, A. Kellmann, F. Tfibel, A. Samat, and R. Guglielmetti, Synthesis Mid photochromic characteristics of l,3-dihydrospiro[2fir-indole-2,3 -[3 /7]pyrimido[5,4-/7[l,4]benzoxa-zines] and 1,3-dihydrospiro[2/f-indole-2,7 -[7/f]thiazolo[5,4-/][l,4]benzoxazines], Helv. Chim. 

Photoinitiated Cationic Polymerization of Unusual Monomers Recently, novel monomers and macromonomers (Chart 11.12), namely, benzoxazines, monothiocarbonates, thiophene, and epoxy and vinyl ether functional polymers were reported to undergo photoinitiated cationic polymerization [2,118], Among them, benzoxazine monomers deserves a special attention as they yield thermosets with several excellent characteristics including heat resistance good flame retardance stable dielectric constants low water absorption and perfect dimensional stability. This type of thermosets is also obtained by thermally activated ring-opening polymerization at elevated temperatures without catalysts [19]. 

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. 

In Table 1 we have listed the reaction yield and the physical characterists of a homologeous series of benzoxazines. These compounds were characterized both by NMR and classical analytical techniques. 

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