Method for preparing retigabine intermediate and method for preparing retigabine

The invention provides a method for preparing a retigabine intermediate. The method comprises the following step of: subjecting p-fluorobenzaldehyde and 2-nitro-1,4-phenylenediamine to a reaction in an alcohol solvent under the action of a reducing agent to generate 2-amino-5-[(4-fluorobenzyl) amino]-1-nitrobenzene, wherein the reducing agent is sodium triacetoxyborohydride or sodium cyanoborohydride. The invention also provides a method for preparing retigabine. The methods do not adopt toxic solvents and expensive catalysts, are economic and environment-friendly, are low in cost and require no complicated post-processing. In addition, because the sodium triacetoxyborohydride or the sodium cyanoborohydride is used as the reducing agent, the complete one-pot reaction is guaranteed, and the yield of the target products can be greatly increased. The experiments show that the methods have the advantage that that the yields of the products are more than 90%.