The invention discloses a preparation method of organic compounds, in particular to 1- (2,6,6- trimethyl cyclohexyl - 3- alkenyl) ethyl ketone, which adopts 4- methyl amyl- 3- alkene - 2- alkone and 1,3- piperylenes as the raw material, with the anhydrous aluminum trichloride as the catalyst, and purifying and preparing through Diels-Alder reaction in the nitryl alkane solvent; wherein, the nitrylalkane solvent is one or several combination solvents among the nitroethane, 1- nitropropanes, and 2- nitropropanes, with a mass ratio of 3 to 5 times of 4- methyl amyl- 3- alkene -2- alkone. The preparation method of organic compounds has the advantages of using nitryl alkane as solvent, distinct enhancement of product efficiency, small solvent toxicity, good solubility, high recycling percentage, easy separation and purification of products, pure product fragrance, and other characteristics.