1.
Prepared according to the accompanying procedure (Paruch, K.; Vyklicky, L.; Katz, T. J. Org. Synth. 2003, 80, 227).
2.
Dichloromethane and triethylamine were distilled from CaH2.
3.
Triisopropyl triflate (97%) was purchased from GSF Chemicals and used as received. The checkers purchased it from Tokyo Chemical Industry.
4.
The product solidifies occasionally.
5.
In two runs, the checkers obtained 15.8 and 15.2 g (99% and 98% yields). The product exhibits the following properties: 1H NMR (CDCl3, 400 MHz) δ: 1.18 (d, 36 H, J = 7.3), 1.35 (m, 6 H), 4.11 (s, 6 H), 4.57 (d, 2 H, J = 1.8), 5.06 (d, 2 H, J = 1.8), 7.90 (dd, 2 H, J = 8.6, 1.6), 8.17 (d, 2 H, J = 8.6), 8.96 (d, 2 H, J = 1.5); 13C NMR (CDCl3, 75 MHz) δ: 12.8, 18.2, 61.0, 90.8, 119.5, 122.0, 124.3, 128.6, 129.1, 135.4, 144.1, 156.4; IR (CCl4) cm−1: 2946, 2868, 1607, 1464, 1322, 1292, 1113, 1015. The checkers reported the following elemental analysis. Calcd. for C30H58O4Si2: C, 71.87; H, 9.21. Found: C, 71.65; H, 9.20.
6.
Heptane was distilled from sodium/benzophenone.
7.
The yield is lower when toluene is used as solvent.
8.
1,4-Benzoquinone (98%, Aldrich) is purified by slurrying it in CH2Cl2 with two times its weight of basic alumina, filtering the mixture through Celite, concentrating the filtrate, and drying the residue under vacuum.
9.
When seven molar equivalents of 1,4-benzoquinone are used, the yield drops to 12%.
10.
Sometimes sublimation of 1,4-benzoquinone plugs the condenser, but turning off the cooling water ameliorates the problem.
11.
The 20-30 mesh sand is obtained from Fisher Scientific.
12.
In two runs the checkers obtained 8.4 and 8.5 g (40% and 42% yields). They found that the product can be purified further by recrystallization from MeOH/EtOAc; mp 272-274°C. IR (CCl4) cm−1: 2948, 2870, 1665, 1610, 1573, 1471, 1385, 1295, 1096. 1H NMR (CDCl3, 400 MHz) δ: 1.20 (d, 18 H, J = 7.5), 1.24 (d, 18 H, J = 7.5), 1.51 (m, 6 H), 4.21 (s, 6 H), 5.92 (d, 2 H, J = 10.1), 6.48 (d, 2 H, J = 10.1), 7.38 (s, 2 H), 8.40 (d, 2 H, J = 8.9), 8.46 (d, 2 H, J = 8.9); 13C NMR (CDCl3, 75 MHz) δ: 13.0, 18.1, 61.2, 107.7, 121.1, 123.3, 125.0, 126.1, 128.0, 129.6, 129.9, 133.0, 134.1, 140.4, 145.3, 157.4, 183.6, 184.6. UV-vis (CH3CN, c = 5.50 × 10−5 M): λmax nm (log ε) 241 (4.54), 285 (4.48), 342 (4.18), 417 (3.76). Anal. Calcd for C50H58O8Si2: C, 71.22; H, 6.93. Found: C, 70.99; H, 6.87. The checkers obtained C, 71.20; H, 6.93.