Patent EA-001784-B1 (EA)
Title: Efficient synthesis of a 1,4-dihydro-2h-3,1-benzoxazin-2-one
Inventor: FREY LISA F
IPC: C07D265/18
Filed: 1998-02-09
Abstract: 1. A process for the preparation of a 1,4-dihydro-2H3,1 -benzoxazin-2-one of the formula   comprising the steps of: 1) adding an aryl chloroformate to a stirring mixture of an amino alcohol of formula   in an organic solvent with a base at a temperature of about 0 degree C to about 25 degree C under an inert atmosphere to produce a carbamate intermediate of formula   wherein R represents the aryl side chain of the chloroformate defined as phenyl or naphthyl, which is optionally substituted with one, two or three substituents selected from the group consisting of halo (F, C1, Br, I), CF3, CO2C1-C6-alkyl, and NO2. 2) stirring the reaction mixture at about 20 degree C to about 25 degree C for about 1 to about 6 hours to complete the formation of the carbamate intermediate; 3) quenching the reaction with water or an aqueous base to produce a biphasic solution containing the 1,4-dihydro-2H-3,1-benzoxazin-2-one in the organic solvent phase; 4) stirring the biphasic mixture at about 20 degree C to about 50 degree C for about 1 to about 6 hours to complete the cyclization to the 1 ,4-dihydro-2H-3, 1-benzoxazin-2-one; and 5) isolating the 1 ,4-dihydro-2H-3,1-benzoxazin-2-one from the organic phase. 2. The process as recited in Claim 1, wherein the base is defined as a solid or solution of KOH, NaOH, LiOH, K2CO3, Na2CO3, Li2CO3, KHCO3, NaHCO3, LiHCO3, or a combination of said bases. 3. The process as recited in Claim 2, wherein the organic solvent is selected form the group consisting of methyl t-butyl ether, toluene, tetrahydrofuran, acetonitrile, dimethylacetamide, N-methylpyrrolidinone, or a combination of said solvents. 4. The process as recited in Claim 3, wherein the aryl group of the aryl chloroformate is defined as phenyl chloroformate, in which the phenyl is optionally substituted with one, two or three substituents selected from the group consisting of: halo (F, C1, Br, I), CF3, and NO2. 5. The process as recited in Claim 4, wherein the base is defined as a solid or solution of KOH, NaOH, K2CO3, Na2CO3, KHCO3, NaHCO3, or a combination of said bases. 6. The process as recited in Claim 5, wherein the aryl group of the aryl chloroformate is defined as 4-nitrophenyl chloroformate. 7. A process for the preparation of a 1,4-dihydro-2H3,1 -benzoxazin-2-one of the formula   comprising the steps of: 1) adding 4-nitrophenyl chloroformate in batches to a stirring mixture of an amino alcohol of formula   in methyl tert-butyl ether with an aqueous solution of KHCO3 at a temperature of about 25 degree C under a nitrogen atmosphere maintaining a pH of between about 8.5 and 4 to produce a carbamate intermediate of formula   2) stirring the reaction mixture at about 20"C to about 25"C for about 2 hours to complete the formation of the carbamate intermediate; 3) quenching the reaction with an aqueous KOH to a pH of about 11 and adding water to produce a biphasic mixture containing the 1 ,4-dihydro-2H-3 ,1 -benzoxazin-2-one in the organic solvent phase; 4) isolating the 1 ,4-dihydro-2H-3 , 1 -benzoxazin-2-one from the organic phase. 8. A process for the preparation of a 1,4-dihydro-2H3,1 -benzoxazin- 2- one of the formula   comprising the steps of: 1) adding an aryl chloroformate to a stirring mixture of an amino alcohol of formula   in an organic solvent at a temperature of about 0 degree C to about 25 degree C under an inert atmosphere to produce a carbamate intermediate of formula   wherein R represents the aryl side chain of the chloroformate, defined as phenyl or naphthyl, which is optionally substituted with one, two or three substituents selected from the group consisting of halo (F, C1, Br, I), CF3, CO2C1-C6-alkyl, and NO2. 2) stirring the reaction mixture at about 20 degree C to about 25 degree C for about 1 to about 6 hours to complete the formation of the carbamate intermediate; 3) quenching the reaction with an aqueous base to produce a -biphasic solution containing the 1,4-dihydro-2H-3,1-benzoxazin-2-one in the organic solvent phase; 4) stirring the biphasic mixture at about 20 degree C to about 50 degree C for about 1 to about 6 hours to complete the cyclization to the 1 ,4-dihydro-2H-3, 1-benzoxazin-2-one; and 5) isolating the 1,4-dihydro-2H-3,1-benzoxazin-2-one from the organic phase. 9. The process as recited in Claim 8, wherein the base is defined as a solid or solution of KOH, NaOH, LiOH, K2CO3, Na2CO3, Li2CO3, KHCO3, NaHCO3, LiHCO3, or a combination of said bases. 10. The process as recited in Claim 9, wherein the organic solvent is selected form the group consisting of methyl t-butyl ether, toluene or a combination of said solvents. 11. The process as recited in Claim 10, wherein the aryl group of the aryl chloroformate is defined as phenyl chloroformate, in which the phenyl is optionally substituted with one, two or three substituents selected from the group consisting of: halo (F, C1, Br, I), CF3, and NO2. 12. The process as recited in Claim11, wherein the base is defined as a solid or solution of KOH, NaOH, K2CO3, Na2CO3, KHCO3, NaHCO3, or a combination of said bases. 13. The process as recited in Claim 12, wherein the aryl group of the aryl chloroformate is defined as 4-nitrophenyl chloroformate. 14. A process for the preparation of a 1,4-dihydro-2H3,1 -benzoxazin-2-one of the formula   comprising the steps of: 1) adding an aryl chloroformate to a stirring mixture of an amino alcohol of formula   in an organic solvent with a base at a temperature of about 0 degree C to about 25 degree C under an inert atmosphere to produce a carbamate intermediate of formula   wherein R represents the aryl side chain of the chloroformate defined as C1-C10-alkyl, which is optionally substituted with one, two or three substituents selected from the group consisting of halo (F, C1, Br, I), CF3, CO2C1-C6-alkyl, and NO2. 2) stirring the reaction mixture at about 20 degree C to about 25 degree C for about 1 to about 30 hours to complete the formation of the carbamate intermediate; 3) isolating the organic phase containing the alkyl carbamate; 4) distilling about 90% to about 95% of the first organic solvent in vacuum and adding a counter solvent to isolate the solid alkyl carbamate; 5) adding a second organic solvent to the solid alkyl carbamate to form an alkyl carbamate solution; 6) reacting the alkyl carbamate solution with a second base at a temperature range of about 20 degree C to about 25 degree C for about 2 hours to about 30 hours to produce the 1 ,4-dihydro-2H-3, 1-benzoxazin-2-one; 7) quenching the reaction mixture with an acid to produce a biphasic solution containing the 1 ,4-dihydro-2H- 3,1-benzoxazin-2-one in the organic solvent phase; 8) isolating the 1,4-dihydro-2H-3,1-benzoxazin-2-one from the organic phase. 15. The process as recited in Claim 14, wherein the first base is defined as a solid or solution of of KOH, NaOH, LiOH, K2CO3, Na2CO3, Li2CO3, KHCO3, NaHCO3, LiHCO3 or a combination of said bases. 16. The process as recited in Claim 15, wherein the first organic solvent is selected form the group consisting of methyl t-butyl ether, toluene, tetrahydrofuran, acetonitrile or a combination of said solvents. 17. The process as recited in Claim 16, wherein the counter solvent is heptane. 18. The process as recited in Claim 17, wherein the second organic solvent is selected form the group consisting of methyl t-butyl ether, toluene, tetrahydrofuran, C1-C6-alkanol, or a combination of said solvents. 19. The process as recited in Claim 18, wherein the second base is defined as a solid or solution of KOC1-C6-alkyl, NaOC1-C6-alkyl, LiOC1-C6-alkyl, KC1-C6-alkyl, NaC1-C6-alkyl, LiC1-C6-alkyl, KHMDS, NaHMDS, LiHMDS, LDA or a combination of said bases. 20. The process as recited in Claim 19, wherein the acid is selected form the group consisting of: HCl, HNO3, H2SO4 and CH3CO2H. 21. The process as recited in Claim 20, comprising the additional step of: crystallizing the alkyl carbamate produced in step 4 from toluene-heptane or methyl t-butyl ether-heptane to produce the desired crystalline alkyl carbamate. 22. The process as recited in Claim 21, wherein the alkyl chloroformate is defined as methyl or ethyl chloroformate. 23. The process as recited in Claim 22, wherein the organic solvent (or solvent mixture) is selected form the group consisting of: methyl t-butyl ether; methyl t-butyl ether and tetrahydrofuran; and methyl t-butyl ether and ethanol. 24. The process as recited in Claim 23, wherein the base is defined as a solid or solution of KHCO3 and KOH, KHCO3 and K2CO3, or KHCO3, and LiO<t>Bu. 25. The process as recited in Claim 23, wherein R, representing the aryl side chain of the chloroformate, is unsubstituted C1-C10 alkyl.