Facile procedures for the synthesis of mono-, di-and triphenylindanee derivatives from the alcohols 1-4 are described thus treatment with 85% H 2 SO 4 , AlCl 3 /CH 3 NO 2 , H 3 PO 4 and/or PPA under varying conditions produced 1,1-dimethyl-3-phenylindanee 6 from 2-methyl-4,4-diphenyl-2-butanol 1, 3,3-dimethyl-1,1-diphenylindanee 9 from 2-methyl-4,4,4-triphenyl-2-butanol 2, 1methyl-1,3-diphenylindanee 12 from 2,4,4-triphenyl-2-butanol 3 and 1,1,3-triphenylindanee 15 from

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... panol 4. The starting and final products were characterized by elemental, IR, 1 H NMR and MS analyses. General Papers ARKIVOC 2009 (xiv) 314-323 applicability and the facility of this ring closure approach, but also proved its dependence on electronic, steric and ring-strain factors. [7] [8] [9] [10] [11] Herein, we describe the synthesis of mono-, di-and triphenylated indane derivatives via intramolecular Friedel-Crafts reactions of alkanols 1-4 (Scheme 1). Scheme 1. Starting alkanols 1-4 Results and Discussion Production of 1,1-dimethyl-3-phenylindane 6 As shown in Table 1 and Scheme 2, reaction of 2-methyl-4,4-diphenyl-2-butanol 1 in the presence of AlCl 3 /CH 3 NO 2 , H 3 PO 4 or PPA gave 1,1-dimethyl-3-phenylindane 6 as a sole product. In the presence of 85% H 2 SO 4 however, the reaction gave 3-methyl-1,1-diphenyl-2butene 7 after 2 hours and a mixture of 6 and 7 after 12 hours. The failure of 85% H 2 SO 4 to induce complete closure of 5 is probably due to the greater tendency, under these conditions, to localize the positive charge on the tertiary center, so elimination to 3-methyl-1,1-diphenyl-2-butene 7 is favored. Scheme 2. Cyclialkylation of 2-methyl-4,4-diphenyl-2-butanol 1. Production of 3,3-dimethyl-1,1-diphenylindane 9 A set of six experiments carefully designed to explore the effect of reaction variables (such as catalyst type, solvent nucleophilicity, time and temperature) on the course of cyclialkylation of 2-methyl-4,4,4-triphenyl-2-butanol 2 were conducted. Indane 9 was obtained as sole product in the presence of AlCl 3 /CH 3 NO 2 , H 3 PO 4 or PPA catalysts. With 85% H 2 SO 4 catalyst, however, varying proportions of 9 and 1,1,1-triphenyl-2-butene 10 were obtained depending on reaction time (Table 1, entries 7-12 and Scheme 3). General Papers ARKIVOC 2009 (xiv) 314-323 Scheme 3. Cyclialkylation of 2-methyl-4,4,4-triphenyl-2-butanol 2. Production of 1-methyl-1,3-diphenylindane 12 This was obtained as a sole product from 2,4,4-triphenyl-2-butanol 3 with either AlCl 3 /CH 3 NO 2 or H 3 PO 4 catalyst. Using 85% H 2 SO 4 as catalyst, however, resulted in pure 1,1,3-triphenyl-2butene 13 after 2 hours of reaction and in a mixture of 12 (38%) and 13 (49%) after 15 hours (Scheme 4 and Table 1 , entry 16). Scheme 4. Cyclialkylation of 2,4,4-triphenyl-2-butanol 3. Production of 1,1,3-triphenylindane 4 Attempted cyclialkylation of 1,1,3,3-tetraphenyl-1-propanol 4 with 85% H 2 SO 4 or AlCl 3 /CH 3 NO 2 catalyst at room temperature failed, giving similar products whose elemental, spectral and chromatographic data confirmed the formation of pure 1,1,3,3-tetraphenylpropene 16 (Scheme 1 and Table 1 , entries 17 and 18). More strenuous conditions were then applied. While treatment of 4 with H 3 PO 4 for 4 hours at 240-260 °C gave a mixture consisting of 15 (27%) and 16 (68%), treatment with PPA at 230-250 °C for 48 hours gave solely 15 (75% yield) ( Table 1 , Entry 19). These results can be attributed to two factors: (i) the steric crowding of the two phenyls encountered in closure of tertiary carbocation 14 to 15 and (ii) the doubly benzylic nature of 14 causes extensive delocalization of the positive charge over the two phenyl groups resulting in a lower energy, and hence a less reactive reaction site in the intermediate cation. The relative retardation influence of these steric and electronic factors on the ring closure step is hard to measure, but it is believed that the steric factor plays the major part. Scheme 5. Cyclialkylation of 1,1,3,3-tetraphenyl-1-propanol 4.