Dibromination of alkenes with LiBr and H₂O₂under mild conditions

Abstract

Activation of H2O2 by LiBr and AcOH is efficiently achieved for dibromination of alkenes in high yields and selectivity.

Efficient Synthesis of Dibromoalkanes and Iodoacetates from Olefins Using ZnAl-XO3--LDHs/LiX (X=Br, I) as Halogen Sources

“…The crude products were purified by column chromatography on silica gel. 1 H NMR spectra were determined on a BRUKER 500 MHz spectrometer and 13 C NMR spectra were recorded at 126 MHz spectrometer in CDCl 3 solutions. Chemical shifts (δ) were referenced to tetramethylsilane (TMS) using the residual solvent signal as internal standard.…”

“…67～ 68 ℃ (lit. [26a] : 65～67 ℃); 1 H NMR (500 MHz, CDCl 3 ) δ: 7.46～7.36 (m, 5H), 5.18 (dd, J＝10.7, 5.4 Hz, 1H), 4.13～4.03 (m, 2H); 13 135.71, 133.50, 132.90, 129.08, 128.19, 127.77, 127.42, 126.90, 126.68, 124.36, 51.36, 34.80 1-Butyl-4-(1,2-dibromoethyl)benzene (2d) [13] : Yellow solid, m.p. 48～50 ℃; 1 H NMR (500 MHz, CDCl 3 ) δ: 7.44～7.40 (m, 2H), 7.37～7.34 (m, 2H), 5.19 (dd, J＝ 10.3, 5.6 Hz, 1H), 4.12～4.04 (m, 2H), 1.35 (s, 9H); 13 C NMR (126 MHz, CDCl 3 ) δ: 152.31,135.54,127.30,125.82,51.26,35.16,34.72,31.24;HRMS (ESI) 1,2-Dibromo-2,3-dihydro-1H-indene (2l): White solid, m.p.…”

“…35～37 ℃ (lit. [26j] : 31～32 ℃); 1 H NMR (500 MHz, CDCl 3 ) δ: 7.45～7.42 (m, 1H), 7.33～7.30 (m, 2H), 7.26～7.23 (m, 1H), 5.34 (d,J＝5.7 Hz,1H), 4.32～4.28 (m, 1H), 3.63～3.58 (m, 1H), 3.27～3.22 (m, 1H); 13 C NMR (126 MHz, CDCl 3 ) δ: 141. 66, 139.74, 128.99, 127.62, 124.56, 124.10, 83.39, 54.50, 40.48; HRMS (ESI) calcd for C 9 H 8 Br 2 (M＋H) ＋ 274.9071, found 274.9069.…”

“…2-Iodo-1- (2-o-tolyl)ethyl acetate (3c) [18] : Yellow oil; 1 H NMR (500 MHz, CDCl 3 ) δ: 7.40～7.36 (m, 1H), 7.28～ 7.23 (m, 2H), 7.22～7.18 (m, 1H), 6.13 (dd, J＝8.5, 5.05 Hz, 1H), 3.48～3.41 (m, 2H), 2.46 (s, 3H), 2.15 (s, 3H); 13C NMR (126 MHz, CDCl 3 ) δ: 169.57, 136.93, 135.22, 130.59, 128.42, 126.32, 125.34, 72.14, 20.88, 19.18, 6.56 ethyl acetate (3d) [25f] : Yellow oil; 1 H NMR (500 MHz, CDCl 3 ) δ: 7.29～7.26 (m,2H),7.22～ 7.19 (m,2H),5.90 (dd,J＝8.05,5.3 Hz,1H),3.53～3.45 (m,2H),2.38 (s,3H), 2.15 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ: 169.51, 138.39, 135.35, 129.21, 126.24, 74.94, 21.10, 20.89, 7.83 [19] : Yellow oil; yield; 1 H NMR (500 MHz, CDCl 3 ) δ: 7.37～7.34 (m, 1H), 7.33～7.27 (m, 2H), 7.26～7.22 (m, 1H), 5.85～5.81 (m, 1H), 3.46～3.43 (m, 2H), 2.16 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ: 169.58, 140.43, 134.63, 129.99, 128.91, 126.54, 124.76, 74.35, 20.98, 7.22 (d, J＝8.3 Hz, 2H), 5.87 (t, J＝6.4 Hz, 1H), 3.88 (s, 3H), 3.44 (d, J＝6.4 Hz, 2H), 2.13 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ: 169.62, 166.48, 143.23, 130.41, 129.95, 126.42, 74.50, 52.21, 20.93, 7.20 169.33, 141.82, 128.42, 127.65, 124.57, 80.74, 26.11, 21.98, 17.30 [25f] : Yellow oil; 1 H NMR (500 MHz, CDCl 3 ) δ: 7.44～7.41 (m, 1H), 7.39～7.34 (m, 1H), 7.31～7.27 (m, 2H), 6.42 (d,J＝ 3.65 Hz,1H), 4.52～4.49 (m, 1H), 3.79～3.74 (m, 1H), 3.37～3.33 (m, 1H), 2.12 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ: 170. 24, 141.97, 138.52, 129.52, 127.46, 125.69, 124.66, 85.56, 43.28, 24.20, 20.90; HRMS (ESI) calcd for C 11 H 11 IO 2 (M＋H) ＋ 302.9882, found 302.9880.…”

“…However, elemental bromine is used for the preparation of these reagents. Alternatively, oxidative brominations such as DMSO/HBr, [12] H 2 O 2 / LiBr, [13] CAN/KBr, [14] 3 BrO -/Br -, [15,1c] and oxone/NH 4 Br [16] continue to garner significant interest.…”