Process for preparing beta-ketoester compound
The present invention relates to a new process for preparing beta-ketoester compound of the following formula (1), which is a useful intermediate for the synthesis of such quinoline antibiotics as Ciprofloxacin, Levofloxacin, Gemifloxacin, Trovafloxacin, etc. The quinoline antibiotics obtained from the above compound of formula (1) show potent antibacterial activity, and so are advantageously used as a therapeutic agent for bacterial infections of humans or animals.
1. A process for preparing a compound of the following formula (1):
in which
R 1 represents C 1 –C 4 -alkyl or benzyl,
X and Y each represent Cl, F, or NO 2 , and
Q represents C—H, C—F, C—NO 2 , or N, characterized in that a nitrile compound of the following formula (2):
in which X, Y, and Q are defined as above, is reacted in a solvent in the presence of zinc metal and a catalytic amount of organic acid or derivative thereof with an alkyl alpha-haloacetate compound of the following formula (5):
in which R 1 is defined as above and W represents Br or I, and then hydrolyzed in the presence of an aqueous acid solution.
2. The process according to claim 1 which proceeds as a one-pot reaction.
3. The process according to claim 1 wherein the solvent is one or more selected from the group consisting of tetrahydrofuran, benzene, toluene, and ether.
4. The process according to claim 3 wherein the solvent is tetrahydrofuran.
5. The process according to anyone of claims 1 to 4 wherein R 1 represents C 1 –C 4 -alkyl in the alkyl alpha-haloacetate compound of formula (5).
6. The process according to claim 5 wherein the alkyl alpha-haloacetate compound of formula (5) is used in an equimolar to 2.0 times molar amount with respect to the compound of formula (2).
7. The process according to claim 1 wherein the zinc metal is used in an equimolar to 2.0 times molar amount with respect to the compound of formula (2).
8. The process according to claim 1 or 7 wherein the zinc metal is in the form of dust or powder.
9. The process according to claim 1 wherein the organic acid or derivative thereof is one or more selected from the group consisting of RCO 2 H, RSO 3 H, RCO 2 (trimethylsilyl) TMS, RSO 3 TMS, and (RSO 3 ) 2 NH, wherein R represents hydrogen; saturated or unsaturated alkyl which has 1 to 6 carbon atoms and which is optionally substituted by halogen; or saturated or unsaturated aryl which has 6 to 12 carbon atoms and which is optionally substituted by halogen.
10. The process according to claim 1 or 9 , the organic acid or derivative thereof is used in a catalytic amount of 0.001 to 0.1 time molar amount with respect to the compound of formula (2).
11. The process according to claim 1 wherein the aqueous acid solution is aqueous hydrochloric acid solution or aqueous sulfuric acid solution.
12. The process according to claim 11 wherein the aqueous acid solution is aqueous hydrochloric acid solution.
13. The process according to claim 11 wherein the acid is used in 2 to 5 times molar amount with respect to the compound of formula (2).
14. The process according to claim 11 wherein the aqueous acid solution is added dropwise at temperatures ranging from 0 to 10° C. and the hydrolysis reaction is carried out at temperatures ranging from 20 to 30° C.
15. The process according to claim 1 wherein a compound of the following formula (2a):
which is the compound of formula (2) wherein X and Y each represent Cl, and Q represents N, is reacted and hydrolyzed to give a solid product, which is then filtered and washed to give a compound of the following formula (1a):
16. The process according to claim 15 wherein the washing is carried out using ethanol or a solvent mixture of ethanol and water.
17. The process according to claim 16 wherein the mixing ratio of the solvent mixture of ethanol and water is 7:3 to 4:1 (v/v).