[CH3:1][C:2]([CH3:9])=[CH:3][CH2:4][CH2:5][CH:6]([OH:8])[CH3:7].[CH:10](=O)/[CH:11]=[CH:12]/[CH3:13]>C1(C)C=CC(S(O)(=O)=O)=CC=1.C1(C)C=CC=CC=1>[CH:2]([CH:3]1[CH2:4][CH2:5][CH:6]([CH3:7])[O:8][CH:10]1[CH:11]=[CH:12][CH3:13])([CH3:9])[CH3:1]6-Methyl-hept-5-en-2-ol (512 g, 3.8 mol, 96%), toluene (750 ml), and p-toluenesulfonic acid (pTSA, 2.6 g) were charged in a flask and heated to 122° C. Crotonaldehyde (350 g, 5 mol) was fed into the mixture for over 3-4 hours at reflux. Water was removed with a Bidwell-Sterling trap. The reaction mixture was aged for 1 hour. Standard addition and gas chromatography (GC) analysis indicated that about 11% of the starting material 6-methyl-hept-5-en-2-ol was left. Additional crotonaldehyde (35 g, 0.5 mol) was added. The reaction mixture was at reflux for another 45 minutes. About 70 ml water was collected and the final temperature was about 118° C. GC analysis indicated that about 8% of the starting material 6-methyl-hept-5-en-2-ol was left. The reaction mixture was quenched with water and wash one time with dilute carbonate solution. The consequent rushover process provided the product 3-isopropyl-6-methyl-2-propenyl-tetrahydro-pyran (493 g) with a boiling point of 109 C at a pressure of 25 mmHg.
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