[CH3:1][C:2]([C:5]1[CH:6]=[C:7]([CH:15]([CH3:17])[CH3:16])[C:8]([OH:14])=[C:9]([CH2:12][OH:13])[C:10]=1[CH3:11])([CH3:4])[CH3:3].[CH3:18][CH:19]1OC(C)OC(C)O1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>O1CCOCC1>[CH3:18][CH:19]1[O:14][C:8]2[C:7]([CH:15]([CH3:17])[CH3:16])=[CH:6][C:5]([C:2]([CH3:1])([CH3:3])[CH3:4])=[C:10]([CH3:11])[C:9]=2[CH2:12][O:13]1A mixture of 5-(1,1-dimethylethyl)-6-methyl-3-(1-methylethyl)-2-hydroxy-benzenemethanol (7.09 g, 0.03 mol), p-dioxane (150 mL), paraldehyde (13.2 g, 0.3 mol) and p-toluenesulfonic acid monohydrate (0.57 g, 0.003 mol) was heated at reflux for 1.5 hours. The mixture was cooled to 25° C., poured onto water (100 mL) and extracted with hexane (3×50 mL). The extracts were washed with saturated sodium bicarbonate solution (2×50 mL), water (4×50 mL), brine (50 mL) and dried (Na2SO4). Evaporation of solvents and distillation of the residue gave 5.56 g (71% yield, GLC purity 99%) of 2,5-dimethyl-6-(1,1-dimethylethyl)-8-(1-methylethyl)-4H-1,3-benzodioxin, bp 110°-120° C., 0.5 mm; 1H-NMR (CDCl3)δ 1.20 (6H, d, J=7 Hz), 1.40 (9H, s), 1.54 (3H, d, J=5 Hz), 2.20 (3 H, s), 2.9-3.5 (1H, m), 4.80 (2H, s), 5.07 (1H, q, J=5 Hz), 7.10 (1H, s); IR (film)νmax 2940, 1585, 1410 cm-1 ; MS m/e 262, 218, 203, 175, 161; UVλmax (ethanol) 225 (ε=6960), 281 (ε=2040).
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