Abstract：4-Bromobenzene carboxylic acid as the starting material,which was acylated to generate acyl chloride.Firstly acyl chloride and N,O-dimethylhydroxylamine hydrochloride reacted to synthesize the amides,which reacted with chlorovinylmagnesium to synthesize alpha, beta unsaturated ketone. At the moment allyl amine was synthesized with pentanal and di-n-propylamine.By Michael addition reaction, alpha, beta unsaturated ketone and allyl amine reacted to synthesize intramolecular aldehyde and ketone,which reacted to synthesize more than 99.5% purity of trans-5-propyl-2-(4′-bromine-phenyl)-tetrahydropyran (3PyPBr)with closed loop reaction and recrystallization with ethanol.