Abstract: The present invention discloses the preparation method of cis-p-menthane-1,8-di-secondary amine compounds and their application in weed control. The preparation method is as follows: cis-p-menthane-1,8-di-Schiff base compounds are used as the raw material, and the reducing agent is added in batches into the raw material in a polar organic solvent at ?10˜50° C. to react for 1˜24 h; after the reaction is complete, the reaction solution is quenched with distilled water and extracted with dichloromethane, and the extract phase is dried with anhydrous sodium sulfate, filtered with a filter and then distilled under reduced pressure to obtain crude cis-p-menthane-1,8-di-secondary amine compounds, which are purified into the pure product through recrystallization or silica gel column chromatography.

Abstract: Disclosed is a process for preparing isopimaric acid, comprising the following steps: First step: dissolving thermally isomerized rosin in acetone, adding in drops a solution of isobutanolamine in acetone to form a precipitate, standing, filtering, washing with ethanol, and drying to obtain crude ammonium salt of isopimaric acid; recrystallizing the crude ammonium salt of isopimaric acid according to multi-recrystallization, and drying to obtain purified crystal of ammonium salt of isopimaric acid; Second step: dissolving the purified crystal of ammonium salt of isopimaric acid obtained in the first step in ether, adding hydrochloric acid in portions until the crystal of ammonium salt of isopimaric acid disappears, removing a water layer and washing the ether layer with water to neutral, evaporating the ether, dissolving the residue in acetone, adding water slowly into the solution dropwise until crystals cease to grow, then filtering and drying to obtain purified isopimaric acid.