Preparation method of 5,5-difluoro-3-substituted piperidine derivative

The invention relates to a preparation method of a 5, 5-difluoro-3-substituted piperidine derivative. The method comprises the following steps: (1) by taking a compound 2 as a starting material, reducing the compound 2 at 0-80 DEG C to generate a compound 3; (2) dehydrating the compound 3 to generate a compound 4; (3) carrying out Pd-C catalysis and H2 reduction on the compound 4 at the temperature of 0-70 DEG C to generate a compound 5; and (4) further reacting the compound 5 to generate the 5, 5-difluoro-3-substituted piperidine derivative 1, and the reaction formula of the derivative 1 is as shown in the specification, wherein R1 is ester group, carboxyl, hydroxymethyl, amino, acetyl amino, trifluoro acetyl amino, benzylamine or a group shown in the description, R3 is C1-C9 alkyl, aryl or benzyl; R2 is hydrogen, C1-C9 alkyl, aryl, hydroxymethyl, benzyl or a group shown in the description, R4 is C1-C9 alkyl, aryl or benzyl, and the groups are not substituted or substituted by one or a plurality of substituents consisting of selected free alkyl, halide alkyl, hydroxy alkyl, halogen, alkoxy or hydroxy.