Synthesis method for preparing SGLT inhibitor intermediate

1. A method for preparing compound 1 and compound 2 having a structure as shown below, wherein the method comprises the following steps:

1) subjecting 2,3-dihydrobenzofuran-7-amine as a raw material to a selective-dibromination with a brominating reagent to obtain 4,6-dibromo-2,3-dihydrobenzofuran-7-amine;

2) subjecting 4,6-dibromo-2,3-dihydrobenzofuran-7-amine obtained in the step 1) to Sandmeyer reaction for chlorination to obtain 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran;

3-1) selectively debrominating from 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran obtained in the step 2) using a strong base, and then adding a formylation reagent to obtain compound 1; and

3-2) selectively debrominating from 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran obtained in the step 2) using a strong base, and then reacting with 4-cyclopropyl benzaldehyde to obtain compound 2.

2. The method according to claim 1 , wherein in the step 1), the brominating reagent is at least one of bromine, N-bromosuccinimide (NBS), and dibromohydantoin.

3. The method according to claim 1 , wherein the selective-dibromination is carried out at a reaction temperature in a range from 10° C. to 20° C.

4. The method according to claim 1 , wherein in the step 2), a reagent used in the Sandmeyer reaction is at least one of hydrochloric acid/sodium nitrite/cuprous chloride system, isoamyl nitrite ester/cupric chloride system, and t-butyl nitrite/cupric chloride system.

5. The method according to claim 1 , wherein in the step 3-1), the strong base is at least one of n-butyllithium, tert-butyllithium, and isopropylmagnesium chloride.

6. The method according to claim 1 , wherein in the step 3-1), the formylation reagent is one of N,N-dimethylformamide, N-formylmorpholine, and ethyl formate.

7. The method according to claim 1 , wherein in the step 3-2), the strong base is at least one of n-butyllithium, tert-butyllithium, and isopropylmagnesium chloride.

8. The method according to claim 2 , wherein the step 1) comprises: filtering after the dibromination, adding the filter cake to a mixed solvent of water and ethyl acetate, followed by sodium hydroxide solution dropwise to adjust pH in a range from 8 to 10, separating and drying the organic layer over anhydrous sodium sulfate, and concentrating the residue under reduced pressure to obtain 4,6-dibromo-2,3-dihydrobenzofuran-7-amine.

9. The method according to claim 4 , wherein the step 2) comprises: adding 4,6-dibromo-2,3-dihydrobenzofuran-7-amine and concentrated hydrochloric acid to a reaction flask and cooling down to a temperature of 0-5° C.; adding sodium nitrite solution dropwise while maintaining at a constant temperature; after the dropwise addition, reacting for 20-60 minutes while maintaining at a constant temperature; then adding cuprous chloride in batches and reacting for 1-3 hours at room temperature; extracting with ethyl acetate, washing the organic layer with sodium hydroxide solution and concentrating to obtain a crude product; and separating and purifying the crude product to obtain 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran.

10. The method according to claim 4 , wherein the step 3-1) comprises: to a reaction flask, adding 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran and tetrahydrofuran, followed by isopropylmagnesium chloride in tetrahydrofuran dropwise under nitrogen protection; after the dropwise addition, stirring for 0.5-1.5 hours while maintaining at a constant temperature; then adding N,N-dimethylformamide dropwise while maintaining at a constant temperature, and continuing to react for 20-60 minutes while maintaining at a constant temperature; pouring the reaction solution into hydrochloric acid, extracting with ethyl acetate, drying the organic layer over anhydrous sodium sulfate; and concentrating and separating to obtain compound 1.

11. The method according to claim 7 , wherein the step 3-2) comprises: adding 4,6-dibromo-7-chloro-2,3-dihydrobenzofuran and tetrahydrofuran to a reaction flask, cooling down to −30° C. under nitrogen protection; adding isopropyl magnesium chloride in tetrahydrofuran dropwise, followed by n-butyllithium in n-hexane dropwise; after the dropwise addition, stirring for 20-60 minutes while maintaining at a constant temperature; then adding 4-cyclopropylbenzaldehyde in tetrahydrofuran dropwise while maintaining at a constant temperature; after the dropwise addition, continuing to react for 20-60 minutes while maintaining at a constant temperature; pouring the reaction solution into hydrochloric acid, extracting with ethyl acetate, and drying the organic layer over anhydrous sodium sulfate; and concentrating, separating and purifying to obtain compound 2.