Method for preparing 2-hydroxyl-4-(2, 3-disubstituted benzyloxy)-5-substituted benzaldehyde derivative
Provided is a method for preparing 2-hydroxy-4-(2, 3-disubstituted benzyloxy)-5-substituted benzaldehyde derivative represented by formula (I). The method comprises the following steps: (1) preparing 3-aryl-2-substituted toluene derivative 2 by using 3-iodo-2-substituted toluene derivative 1 and aryl boronic acid 5 or aryl boronate as starting materials; (2) preparing a benzyl halide derivative 3 by using 3-aryl-2-substituted toluene derivative 2 as starting materials; and (3) preparing 4-(2, 3-disubstituted benzyloxy)-2-hydroxy-5-substituted benzaldehyde derivative (I) by using benzyl halide derivative 3 and 2,4-dihydroxy-5-substituted benzaldehyde 6.
1. A method for preparing 4-(2, 3-disubstituted benzyloxy)-2-hydroxy-5-substituted benzaldehyde derivative (I):
wherein the method comprises the following steps:
1) preparing 3-aryl-2-substituted toluene derivative 2 from 3-iodo-2-substituted toluene derivative 1 and aryl boronic acid 5, or an aryl boronate thereof, as starting materials:
wherein “a” means that 3-iodo-2-substituted toluene derivative 1 and aryl boronic acid 5, or an aryl boronate thereof, are subjected to a Suzuki-Miyaura coupling reaction to form 3-aryl-2-substituted toluene derivative 2 in the presence of a palladium catalyst and a base;
2) preparing benzyl halide derivative 3 from 3-aryl-2-substituted toluene derivative 2 as a starting material:
wherein “b” means that 3-aryl-2-substituted toluene derivative 2 is reacted with a halogenating agent under radical-initiating condition to prepare a benzyl halide derivative 3;
3) preparing 4-(2, 3-disubstituted benzyloxy)-2-hydroxy-5-substituted benzaldehyde derivative (I) from benzyl halide derivative 3 and 2,4-dihydroxy-5-substituted benzaldehyde 6 as starting materials:
wherein “c” means that benzyl halide derivative 3 is reacted with 2, 4-dihydroxy-5-substituted benzaldehyde 6 in a weak basic condition to selectively prepare a 4-(2, 3-disubstituted benzyloxy)-2-hydroxy-5-substituted benzaldehyde derivative (I);
wherein:
R 1 is selected from fluorine, chlorine, bromine, methyl, and cyano;
R 2 is selected from
R 3 is selected from hydrogen, methyl, ethyl, fluorine, chlorine, and bromine;
X selected from bromine, chlorine, and iodine.
2. The method according to claim 1 , wherein the palladium catalyst is selected from zero-valent palladium and divalent palladium compounds.
3. The method according to claim 2 , wherein the zero-valent palladium catalyst is selected from triphenylphosphine palladium and tetrakis(triphenylphosphine)palladium, and the divalent palladium catalyst is PdCl 2 (dppf).
4. The method according to claim 1 , wherein the base is selected from alkali metal carbonate and alkali metal acetate.
5. The method according to claim 4 , wherein the alkali metal carbonate is selected from cesium carbonate, potassium carbonate, and sodium carbonate, and the alkali metal acetate is selected from sodium acetate and potassium acetate.
6. The method according to claim 1 , wherein the halogenating agent is selected from N-bromosuccinimide, N-chlorosuccinimide, phenyltrimethylammonium tribromide, and elemental bromine.
7. The method according to claim 1 , wherein the radical initiating condition is the addition of a radical initiator, or light, or a combination thereof.
8. The method according to claim 7 , wherein the radical initiator is selected from benzoyl peroxide and m-chloroperoxybenzoic acid.
9. The method according to claim 1 , wherein the weak base condition is the addition of an alkali metal hydrogen carbonate or an alkali metal acetate.
10. The method according to claim 9 , wherein the alkali metal hydrogen carbonate is selected from sodium hydrogen carbonate and potassium hydrogen carbonate.