2,3-DIHYDROTHIENO[3,4-B][1,4]DIOXINE-5-CARBALDEHYDE synthesis

Yield:204905-77-1 22% ，211235-87-9 43%

Reaction Conditions:

Stage #1: bromodichloromethane;3,4-(ethylenedioxy)thiophenewith 1,1'-bis-(diphenylphosphino)ferrocene;potassium phosphate;palladium diacetate;acetic anhydride;silver carbonate in acetonitrile at 60; for 48 h;Schlenk technique;Inert atmosphere;
Stage #2: with hydrogenchloride in dichloromethane at 30;Overall yield = 66 %;

Steps:

General Procedure

General procedure: To a 50 mL of Schlenk tube were added 1 or 3 (0.2 mmol, 1.0 equiv), Pd(OAc)2 (10 mol%), dppf (10 mol%) under air, followed by K3PO4·3H2O (0.3 mmol, 1.5 equiv) and Ag2CO3 (0.3 mmol, 1.5 equiv) . The mixture was then evacuated and back filled with N2 (3 times). Bromodichoromethane (0.4 mmol, 2.0 equiv), Ac2O (2 mmol, 190 uL) and CH3CN (1 mL) were added subsequently. The Schlenk tube was screw capped and put into a preheated oil bath (60 °C). After stirring for 24 hours, the reaction mixture was cooled to room temperature, diluted with CH2Cl2 and Ethyl Acetate, then filtered with a pad of silica gel. The isolated yield was given by a hydrolysis pathway, in which the concentrated reaction mixture was diluted with 5 mL CH2Cl2 and 10 mL 3 N HCl and stirred over night. The reaction mixture was extracted with dichloromethane (3 times) and the solvent was removed under rotary evaporation. The residue was then purified by a preparative TLC to give product 2 or 4.

References:

Bao, Yan;Wang, Jian-Yong;Zhang, Ya-Xuan;Li, Yan;Wang, Xi-Sheng [Tetrahedron Letters,2018,vol. 59,# 32,p. 3147 - 3150] Location in patent:supporting information