Preparation method of betamethasone rearrangement substance and betamethasone rearrangement substance

The invention provides a preparation method and device of betamethasone rearrangement substance, and belongs to the field of chemical engineering. The preparation method of betamethasone rearrangementsubstance provided by the invention comprises the steps of under the protection of inert gas, mixing a compound (I), methanol, dimethyl sulfoxide and sodium methoxide, reacting at the reaction temperature of 30-45 DEG C for 1-3 hours to obtain a reaction solution of a compound (II), directly adding trimethyl phosphite to the reaction solution, and reacting at the reaction temperature of 40-50 DEGC for 4-8 hours to obtain the betamethasone rearrangement substance (III), and adding dimethyl sulfoxide into a reaction system, so that the reaction activity of sodium methoxide is remarkably improved, the reaction time is shortened, and the reaction energy consumption and cost are reduced; and heating reflux is not needed, pollution and waste caused by volatilization of a large amount of trimethyl phosphite are avoided