Synthesis of 3,3-Dimethyl-5-methoxy-l-indanone and 9,9-Dimethyl-2-methoxy-5-benzosuberone

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Abstract
In connect ion with synthetic studies towards tricyclovetivene1 and hinschalene2 class of sesquiterpenes, w e required adequate quan-tities of 3,3-dimethyl-5-methoxy-1-indanone (1) and 9,9-dimethyl-2-methoxy-5-benzosuberone (2) as intermediates. The search of the literature revealed that a onestep Synthesis of the indanone 1 has been reported3 through Friedel-Crafts reaction of anisole with α, β-dhethylacryloyl chloride in the presence of anhydrous AlC13. The reported procedure, however, yielded ii our hands only the acrylo-phenone 3 in 72% yield, b.p. 133–132°C/1 mm; 1R (CHCI3) 1665 (s) and 1600 (s) cm−1; 1H-NMR (CC14) δ 7.85–6.7 (m, 4H), 6.5 (m, 1H), 3.77 (s, 3H), 2.15 (d, 3H, J = 1 Hz), 1.95 (d, 3H, J = 1 Hz). Similar observation has been reported recently by Kasturi et.al4. Although acid-catalysed cyclisation of several acrylophenones to indanones have been reported5, all our attempts to cyclise the acrylophenone 3 failed. In the present communication, we wish to report convenient Syntheses of the indanone 1 and the benzosuberone 2 from a common intermediate 14. A synthesis of 2 involving ring expansion of 4,4-dimethyl-6-methoxy-1-tetralone has recently been reported6.