1,1-Diphenylethylene → HCID 71076480, compound

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Reaction Steps

To a flame-dried round bottom flask kept under a dry atmosphere of argon, was added Rh2(RDOSP)4 (0.01 equiv., 382 mg), 1,1-diphenylethlyene 11 (2.32 equiv., 8.16 mL), and dry degassed pentane (100 mL). A solution of freshly prepared methyl 2-(4-bromophenyl)-2-diazoacetate 12 (1.0 equiv., 5.1 g) in dry, degassed pentane (150 mL) was added to the former solution drop-wise over 3 hours at room temperature. The mixture was allowed to stir overnight, and then concentrated in vacuo. The crude material was purified using flash column chromatography eluting with a 50:1 mixture of hexanes/ethyl acetate to provide the desired product as a white foam (7.2 g, 88% yield, 98% ee). mp: 82-85° C.; Rf=0.55 (hexanes/ethyl acetate=7/1); [α]20 D −289.2° (c=1.17, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.48-7.47 (m, 2H), 7.35-7.31 (m, 2H), 7.27-7.18 (m, 5H), 7.02-6.97 (m, 5H), 3.34 (s, 3H), 2.68 (d, J=5.5 Hz, 1H), 2.39 (d, J=5.9 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 170.9, 141.7, 139.1, 134.8, 133.5, 130.6, 129.8, 128.5, 128.3, 127.7, 126.9, 126.3, 121.1, 52.2, 44.6, 42.4, 22.6; IR (neat): 3057, 3024, 2947, 1724, 1490, 1217; HRMS (APCI) calcd for C23H20BrO2 (M+H)+ 407.06412. found 407.06432; HPLC (S,S-Whelk, 5% isopropanol in hexane, 0.8 mL/min, 1 mg/mL, 60 min, UV 254 nm) retention times of 10.6 min (major) and 50.9 min (minor), 98% ee. (S)-methyl 1-(4-bromophenyl)-2,2-diphenylcyclopropanecarboxylate was prepared by the same procedure with Rh2(S-DOSP)4 as the catalyst, [α]20D: 219.6° (c=1.32, CHCl3).

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