Process for the preparation of isoflavones

1. A process for the preparation of 2H-isoflavones of formula I which process comprises the reaction of a 2-hydroxyaryl alkyl ketone of formula II in the presence of a base with a formic-sulfuric anhydride salt of formula III and which reaction is followed by neutralization, wherein

formula I is

wherein

R3 is hydrogen, hydroxyl or alkoxyl, alkyl, substituted alkyl, or unsaturated alkyl, when R3 is not hydrogen or hydroxyl then the atoms comprising the substituent may comprise a heterocyclic ring of oxygen and carbon atoms attached to position 4 of the ring which rings may be saturated or unsaturated and optionally substituted with alkyl groups;

R4 is hydrogen, hydroxy or alkoxyl, when R4 is alkoxyl then the elements of the substituent may comprise a heterocyclic ring of carbon and oxygen atoms attached to positions 3 or 5 which may be saturated or unsaturated and optionally substituted with alkyl groups;

R5 is hydrogen, hydroxyl, alkoxyl, alkyl, substituted alkyl, or unsaturated alkyl, when R5 is not hydrogen or hydroxyl then the atoms of the substituent may comprise a heterocyclic ring of carbon and oxygen atoms attached to the ring at position 4 to form saturated or unsaturated rings such methylenedioxy or dihydofuran, dihydropyran, or pyrene rings which rings themselves may be substituted with alkyl groups;

R6 is hydrogen, hydroxyl, alkoxyl, alkyl or substituted alkyl;

R2′ is hydrogen, hydroxyl, alkoxyl, alkyl, substituted alkyl, or unsaturated alkyl;

R3′ is hydrogen, hydroxyl, alkoxyl, alkyl, substituted alkyl or unsaturated alkyl, when R3′ is not hydrogen or hydroxyl, the atoms of the substituent may comprise a heterocyclic ring of carbon and oxygen atoms attached to position 2′ or 4′ which ring maybe saturated or unsaturated and may be substituted with alkyl groups;

R4′ is hydrogen, hydroxyl, or alkoxyl, when R4′ is not hydrogen or hydroxyl the elements of the substituent may comprise a heterocyclic ring of carbon and oxygen which are attached at position 3′ or 5′, which ring may be saturated or unsaturated and is optionally substituted with alkyl groups;

R5′ is hydrogen, hydroxyl, alkoxyl, alkyl, substituted alkyl or unsaturated alkyl, when R5′ is not hydrogen or hydroxyl, the atoms of the substituent may comprise a heterocyclic ring of carbon and oxygen atoms attached to position 4′, which ring may be saturated or unsaturated and may be substituted with alkyl groups;

R6′ is hydrogen, hydroxyl, alkoxyl, alkyl, substituted alkyl, or unsaturated alkyl;

formula II is

wherein the substituents have the meaning as defined above; and

formula III is

wherein

X is a metallic cation, ammonium, an amine salt, salt of a heterocyclic base, quaternary ammonium or phosphonium salt including polymeric or polymer bound forms thereof;

n is an average number of 1 to 4.

2. A process according to claim 1 which comprises

(a) reaction of a mixture of a 2-hydroxyaryl alkyl ketone of formula II with a suitable base in a suitable solvent,

(b) reaction of the ketone salt with a preformed salt of formic-sulfuric anhydride of formula III,

(c) neutralizing the reaction mixture with a suitable acid, and

(d) separating and isolating the isoflavone.

3. The process according to claim 1 wherein the base is selected from the group consisting of sodium carbonate, potassium carbonate, calcium carbonate, triethylamine, tributylamine, and di-isopropylethylamine.

4. The process according to claim 1 wherein the counterion of the formic-sulfuric anhydride of formula III is sodium, potassium, calcium, triethylammonium, tributylammonium or di-isopropylethyl ammonium.

5. The process according to claim 1 wherein the process is performed at a temperature in the range of from −20° C. to +20° C., with an optional heating of up to 100° C.

6. The process according to claim 1 wherein R4 and R6 are hydroxyl.

7. The process according to claim 1 wherein R4, R6 and R4′ are hydroxyl.

8. The process according to claim 2 wherein the base is selected from the group consisting of sodium carbonate, potassium carbonate, calcium carbonate, triethylamine, tributylamine, and di-isopropylethylamine.

9. The process according to claim 2 wherein the counterion of the formic-sulfuric anhydride of formula III is sodium, potassium, calcium, triethylammonium, tributylammonium or di-isopropylethyl ammonium.

10. The process according to claim 3 wherein the counterion of the formic-sulfuric anhydride of formula III is sodium, potassium, calcium, triethylammonium, tributylammonium or di-isopropylethyl ammonium.

11. The process according to claim 8 wherein the counterion of the formic-sulfuric anhydride of formula III is sodium, potassium, calcium, triethylammonium, tributylammonium or di-isopropylethyl ammonium.

12. The process according to claim 2 wherein the process is performed at a temperature in the range of from −20° C. to +20° C., with an optionally heating of up to 100° C.

13. The process according to claim 3 wherein the process is performed at a temperature in the range of from −20° C. to +20° C., with an optionally heating of up to 100° C.

14. The process according to claim 4 wherein the process is performed at a temperature in the range of from −20° C. to +20° C., with an optionally heating of up to 100° C.

15. The process according to claim 2 wherein the solvent is an ether, an ester, or an amide.

16. The process according to claim 2 wherein R4 and R6 are hydroxyl.

17. The process according to claim 3 wherein R4 and R6 are hydroxyl.

18. The process according to claim 2 wherein R4, R6 and R4′ are hydroxyl.