Journal of Chemistry

Research Article

Preparation of α-Bromoketones Involving the Reaction of Enol Triethyl Borates with N-Bromosuccinimide

Table 1

Results of α-bromination of ketones.
EntryStarting materialProductYielddr %
1294107.fig.001a294107.fig.001b55%a100
2294107.fig.002a294107.fig.002b87%b100
3294107.fig.003a294107.fig.003b90%c100
4294107.fig.004a294107.fig.004b90%d90 : 10
5294107.fig.005a294107.fig.005b85%e50 : 50
6294107.fig.006a294107.fig.006b90%f75 : 25
7294107.fig.007a294107.fig.007b30%—
8294107.fig.008Mixture of products——
aThe selected spectral data of (1S,6R,7aS)-tert-butoxyheksahydro-6-bromo-7a-methyl-1H-inden-5-one (1A): mp (CH2Cl2/hexane) 88–91°C; IR (CHCl3) ν max(cm−1) 1725, 1193; 1H NMR (400 MHz, CDCl3): δ H 4.81 (1H, dd, ,  Hz, CH–Br), 3.52 (1H, dd, ,  Hz, CH–OBut), 1.15 (9H, s, OC(CH 3)3), 1.06 (3H, s, CH 3); 13C NMR (ppm): 201.3 (C), 78.6 (CH), 72.8 (C), 54.1 (C), 48.5 (CH2), 45.1 (CH), 45.0 (C), 41.7 (CH2), 32.1 (CH2), 28.6 (CH3 × 3), 25.4 (CH2), 10.9 (CH3); HRMS: calculated 325.0779, found 325.0779 for C14H23O2BrNa.
bData of 2α-bromocholestan-3-one (2A) have been found to be identical with those reported [3].
cThe selected spectral data of 4β-bromocoprostan-3-one (3A): mp (CH2Cl2/hexane) 93–95°C; IR (CHCl3) ν max (cm−1) 1726, 1468, 555; 1H NMR (400 MHz, CDCl3): δ H 4.98 (1H, d,  Hz, CH–Br), 2.95 (1H, m), 2.50 (1H, d,  Hz, CH 3), 1.08 (3H, s, CH 3), 0.90 (3H, d,  Hz, CH 3), 0.87 (3H, d,  Hz, CH 3), 0.69 (3H, s, CH 3); 13C NMR (ppm): 202.5 (C), 60.05 (CH), 56.4 (CH), 56.3 (CH), 54.2 (CH), 42.7 (C), 41.9 (CH), 39.9 (CH2), 39.5 (CH2), 38.3 (C), 36.7 (CH2), 36.5 (CH2), 36.1 (CH2), 35.7 (CH), 35.6 (CH), 28.2 (CH2), 27.9 (CH), 25.6 (CH2), 25.1 (CH2), 24.1 (CH2), 23.8 (CH2), 23.2 (CH3), 22.8 (CH3), 22.5 (CH3), 21.2 (CH2), 18.6 (CH3), 12.0 (CH3); HRMS: calculated 487.2551, found 487.2545 for C27H45OBrNa.
dThe selected spectral data of 4β-bromosmilagenin (4A): mp (CH2Cl2/hexane) 135-136°C; IR (CHCl3) ν max (cm−1) 1727, 1179; 1H NMR (400 MHz, CDCl3): 4.96 (1H, d,  Hz, CH–Br), 4.41 (1H, m, H16), 3.48 (1H, m, H26), 3.37 (1H, m, H26), 1.10 (1H, s, CH 3), 0.97 (1H, d,  Hz, CH 3), 0.80 (1H, s, CH 3), 0.79 (1H, d,  Hz, CH 3); 13C NMR (ppm): 202.2 (C), 109.2 (C), 80.7 (CH), 66.9 (CH2), 62.2 (CH), 59.8 (CH), 56.2 (CH), 54.1 (CH), 42.0 (CH), 42.0 (CH), 40,7 (C), 40.0 (CH2), 38.3 (C), 36.7 (CH2), 36.5 (CH2), 35.3 (CH), 31.7 (CH2), 31.4 (CH2), 30.2 (CH), 28.8 (CH2), 25.5 (CH2), 25.3 (CH2), 23.2 (CH3), 21.1 (CH2), 17.1 (CH3), 16.4 (CH3), 14.4 (CH3); HRMS: calculated 515.2137, found 515.2135 for C27H41O3BrNa.
eSpectral data identical with those from [4].
fSpectral data identical with those from Spectra Database for Organic Compounds (SDBS), number 4818. Mixture of bromides 6A in ratio 25 : 75, respectively, α-bromo : β-bromo; HRMS: calculated 253.0204, found 253.0201 for C10H15OBrNa.