Method of preparing benzoxazines
View Patent ↗This invention relates to a novel synthesis for the preparation of benzoxazine components from phenolic components, aldehyde components, and amine components in a solvent other than toluene.
1. A method for preparing a 1,3-benzoxazine comprising:
(a) preparing a reaction mixture containing as reactants (i) a phenolic component; (ii) a primary amine component; and (iii) an aldehyde component in an alkyl acetate solvent; and
(b) bringing the reactants and solvent to a temperature at which the reactants combine chemically and maintaining them at that temperature for a time sufficient to form the benzoxazine.
2. The method of claim 1 , wherein the alkyl ester solvent is selected from the group consisting of ethyl acetate, propyl acetate, isopropyl acetate and propyl formate.
3. The method of claim 1 , further comprising washing the reaction mixture of step (b) with aqueous alkali.
4. The method of claim 1 further comprising washing the reaction mixture of step (b) with water.
5. The method of claim 1 , wherein the benzoxazine is formed in a yield of about 90% or better.
6. The method of claim 1 wherein the temperature in step (b) is about 65° C. or more.
7. The method of claim 1 , wherein the reaction occurs within a period of time of 5 hours.
8. The method of claim 1 , wherein the solvent is removed at an elevated temperature.
9. The method of claim 8 , wherein the temperature is about 70° C.
10. The method of claim 1 , wherein the benzoxazine may be embraced by one or more of the following structures:
wherein o is 1-4, X is selected from direct bond (when o is 2), alkyl (when o is 1), alkylene (when o is 2-4), carbonyl (when o is 2), thiol (when o is 1), thioether (when o is 2), sulfoxide,(when o is 2), and sulfone (when o is 2), R 1 is selected from hydrogen, alkyl, alkenyl and aryl, and R 4 is selected from hydrogen, halogen, alkyl and alkenyl; or
wherein p is 2, Y is selected from biphenyl (when p is 2), diphenyl methane (when p is 2), diphenyl isopropane (when p is 2), diphenyl sulfide (when p is 2), diphenyl sulfoxide (when p is 2), diphenyl sulfone (when p is 2), and diphenyl ketone (when p is 2), and R 4 is selected from hydrogen, halogen, alkyl and alkenyl.
11. The method of claim 1 , wherein the time is between about 0.5 to about 30 minutes.