Supplementary Information
Synthesis of alcohols 1,2 and ketones 1,2
Alcohol 1 (1,2: 4,5-Di-O-isopropylidene-fructose):
The compound fructose (100mmol, 18 g) was added intoa 250 ml round-bottom flask filled with 170 ml of dry acetone, then dropwise added slowly with 9 ml of concentrated sulfuric acid at room temperature (or with 6.7 ml of perchloric acid at 0 °C) while stirring. The resulting mixture was magnetically stirred at the given temperaturefor 18 h; bsubsequently，the pH of the solution was adjusted to 7-8 with appropriate amount of ammonia water (NH3·H2O). After that, the solvent was evaporated off by a rotary evaporator at 30 °C to receive a coarse product, then a coarse productwas washed with distilled water and n-hexane, which was further re-crystallized in a mixed solvent of n-hexane and dichloromethane (volume ratio4:1) to obtain pure white acerose crystal alcohol 1 with a yield of 80% (or 67.2%) (Table 1’).
Alcohol 1: M.p.: 114.97°C; IR (KBr) (cm1): 3462, v (OH); 10001300, v (C-O-C); 1H-NMR (CDCl3) (600 MHz): 4.22(dd, J=6.0, 1.8Hz, 1H), 4.19(d, J=9.0Hz, 1H), 4.14 (dd, J=7.2, 5.4Hz, 1H), 4.11(d, J=2.4Hz, 1H), 4.02(d, J=13.2Hz, 1H), 3.99(d, J=9.0Hz, 1H), 3.67(d, J=6.6Hz, 1H), 2.18(s, 1H), 1.54(s, 3H), 1.52(s, 3H), 1.45(s, 3H), 1.38(s, 3H);13C1H-NMR (CDCl3) (150 MHz):111.942(C-10), 109.477(C-7), 104.732(C-5), 77.212(C-3), 73.508(C-6), 72.489(C-4), 70.502(C-1), 60.982(C-2), 27.995(C-11,C-12), 26.431(C-8), 26.027(C-9).
Alcohol 2 (1,2:4,5-Di-O-cyclohexylidene-fructose):
The compound fructose (100 mmol, 18 g) was added into a 100ml round-bottom flask filled with 50 ml of dry cyclohexanone, then dripped slowly with 5 ml of concentrated sulfuric acid at room temperature (or with 6.7 ml of perchloric acid at 0 °C) while stirring. The resulting mixture was magnetically stirred at the given temperature for 12 h;thereafter, the pH of the solution was adjusted to 7-8 with ammonia water (NH3·H2O). A coarse product was recovered by filtration, followed by washing with distilled water and n-hexane to receive white solid, which was finally re-crystallized in a mixed solvent of n-hexane and dichloromethane (volume ratio4:1) to obtain pure white acerose crystal alcohol2with a yield of 65.5% (or 40.1%) (Table1’).
Alcohol 2: M.p.: 150.97 °C; IR (KBr) (cm1): 3471, v (OH); 10001300, v (C-O-C); 1H-NMR (CDCl3) (600 MHz): 4.17(d J=8.4Hz, 1H), 4.16(d, J=9.0Hz, 1H), 4.14 (dd, J=31.2Hz,18.6Hz, 1H), 4.05(d, J=36.0Hz, 1H), 4.00(dd, J=18.6Hz, J=31.2Hz, 1H), 3.96(d, J=8.4Hz, 1H), 3.64(d, J=6.6Hz, 1H), 2.17(s, 1H), 1.73-1.59(m,20H);13C1H-NMR(CDCl3)(150MHz): 112.75(C-13), 110.324(C-5), 104.439(C-7), 72.646(C-2),71.891(C-3), 71.010(C-6), 69.087(C-4), 61.111(C-1), 36.058(C-18), 36.039(C-14), 36.009(C-8), 35.978(C-12), 25.199(C-16), 25.184(C-10), 24.131(C-17), 24.097(C-15), 24.074(C-11), 24.039(C-9).
Synthesis of ketone compounds 1 and 2
The preparation of PCC oxidant was carried out in the following procedure. One hundred grams of CrO3 (1.0 mol) was slowly added into a stirred solution of 6 M HCl (1.1 mol, 184 ml) in a 500 mlglass beaker under mechanical agitation. After being vigorously agitated for 5 min, the solution was cooled down to 0 °Cwith a salt-ice bath, followed by a slow addition of 79.10 gof pyridine (1.0 mol) over 10 min. A vast quantity of orange precipitate appeared which then underwent a speedy filtration at 0 °Cwith Buchner funnel. The recovered orange solid was treated by drying in vacuum at 40 °Cfor 72 h to obtain anorange solidproduct with a yield of 84.4%.IR (KBr) (cm1):3223, 3159, 3062, 2978, 2856, 2025, 1907, 1631, 606, 1537, 1485, 1377, 1330, 1249, 1200, 1167, 1053, 894, 748, 675, 607, 439.
The oxidation from alcohols to ketones by thus-synthesized PCC was carried out in the following procedure. Five grams of 3Åmolecular sieve powder that had been predried in a vacuum oven at 200 °C for 24 h was added into the solution consisting of 4.5 mmol of white acerose crystal alcohols (1.18 g of alcohol1or 1.55 gof alcohol2) and300 ml of dichloromethane in a 500 mlthree-necked flask under stirring. Then, 3.24 g of PCC dried in vacuum at 40 °C for 72 h was added in batches at room temperature into the above mixture over 30 min, accompanied with a color change of the reaction mixture from khaki to shadowy. The reaction was maintained for 5 h while stirring, then added with 200 ml of ethyl ether, followed by a filtration with a core funnel. The residue was scrubbed with 100 ml of ethyl ether and filtrated again. The combined filtrate underwent a solvent evaporation on a rotary evaporator at 30°Cto receive a coarseproduct, which was then dissolved into dichloromethane. The purification of the product was conducted on a silica gel column, in which a mixture of n-hexane and ethyl ether (volume ratio1:1) was used as the eluent. After the solvent in the effluent was evaporated off to obtain leuco-hyalo-crystal (ketone 1) or white crystal (ketone 2), which was further re-crystallized in the mixture of n-hexane and dichloromethane (volume ratio4:1) to yield pure transparent sheet crystal ketone1with a yield of 92.0% orsheet crystal ketone2with a yield of 88.0% (Table1’).
Ketone 1 (1,2:4,5-Di-O-isopropylidene-erythro-2,3-hexdiuro-2,6-pyranose): M.p.: 99.06°C; IR (KBr) (cm1): 1751, v (C=O); 1H-NMR (CDCl3) (600 MHz): 4.73(d, J=5.4Hz, 1H), 4.62(d, J=9.6Hz, 1H), 4.55(ddd, J=5.4, 0.6, 0.6Hz1H), 4.39(ddd, J=11.4, 2.4, 1.8Hz, 1H), 4.12(d, J=13.8Hz, 1H), 3.99(d, J=9Hz, 1H), 1.55(s, 3H), 1.46(s, 3H), 1.40(s, 6H);13C1H-NMR (CDCl3) (150 MHz): 196.90(C-4), 113.76(C-5), 110.57(C-10), 104.63(C-7), 77.87(C-2), 75.82(C-6), 69.93(C-3), 60.02(C-1), 27.10(C-11), 26.45(C-12), 26.00(C-8), 25.95(C-9).
Ketone 2 (1,2:4,5-Di-O-cyclohexylidene-erythro-2,3-hexdiuro-2,6-pyranose): M.p.: 152°C; IR (KBr) (cm1): 1748, v (C=O); 1H-NMR (CDCl3) (600 MHz): 4.75(d, J=5.4Hz, 1H), 4.59(d, J=1.8Hz, 1H), 4.55(d, J=1.2Hz1H), 4.39(dd, J=2.4, 1.8Hz, 1H), 4.14(d, J=13.2Hz, 1H), 3.98(d, J=9.6Hz, 1H), 1.80(d, J=6Hz , 1H), 1.79(d, J=6.6Hz, 1H), 1.70(d, J=5.4Hz, 1H), 1.69(d, J=7.8Hz, 1H),1.69(d, J=2.4Hz, 1H), 1.67(d, J=5.4Hz, 1H), 1.67(d, J=5.4Hz, 1H), 1.66(d, J=4.8Hz , 1H), 1.65(d, J=9.6Hz, 1H), 1.64(d, J=6.6Hz, 1H), 1.63(d, J=3.6Hz1H),1.62(d, J=5.4Hz, 1H), 1.61(d, J=5.4Hz, 1H), 1.60(d, J=5.4Hz , 1H), 1.59(d, J=5.4Hz, 1H), 1.57(d, J=10.8Hz, 1H), 1.56(d, J=9.0Hz1H), 1.55(d, J=7.2Hz, 1H), 1.43(d, J=5.4Hz, 1H), 1.41(d, J=4.8Hz, 1H);13C1H-NMR (CDCl3)(150MHz): 197.517(C-4), 114.806(C-5), 111.530(C-13), 103.947(C-7), 77.788(C-2), 75.728(C-6), 69.793(C-3), 60.467(C-1), 36.940(C-18), 36.356(C-14), 35.654(C-12), 35.494(C-8), 25.111(C-16), 25.073(C-10), 24.158(C-17), 24.108(C-15), 23.955(C-11), 24.910(C-9).
Structural characterization of alcohols 1,2 and ketones 1,2
Figure 1’ shows the IR spectra of raw material fructose, alcohols 1, 2 and ketones 1, 2. For as-prepared alcohols 1 and 2, a sharp absorbance band, attributed to isolated –OH groups, appears at 3462 cm-1 for alcohol 1 and at 3471 cm-1 for alcohol 2, respectively, obviously different from broad band at 33003600 cm-1 for fructose assigned to associated hydroxyls with different degrees of hydrogen bonding. Some new vibration bands emerge at 10001300 cm-1 attributed to C–O–C bond and 29002991 cm-1 to –CH3 and –CH2 bonds for alcohol 1, and at 11201300 cm-1 assigned to C–O–C bond and 29392850 cm-1 to –CH2 bonds for alcohol 2, respectively.
For alcohol 1, one 1H NMR peak at 2.18 ppm is assigned to OH proton, with an intensity much weaker than that of OH protons of raw material fructose. The signals at 1.381.54 ppm are attributedto the protons of CH3. And, we can also observe from 13C NMRspectrum of alcohol 1thatsome new peaks appear at 26.0227.99 ppm, different from 13C NMRspectrum of fructose, due to the carbon signal of –CH3 groups. Similarly, in the 1H NMR spectrum of alcohol 2, one peak appears at 2.17 ppm assigned to OH proton, with intensity much weaker than that of OH protons of fructose. The peaks at 1.301.74 ppm are attributedto the protons of CH2. The 13C NMR spectrum of alcohol shows some new peaks at 24.03936.058 ppm, which cannot be found in that of Fructose, assigned to the carbon signal of –CH2 groups. The above resultsindicate the occurrence of the catalytic condensation reaction between fructose andeither acetone or cyclohexanone.
As illustrated in Scheme 1’, alcohols 1,2 were oxidized by PCC to ketones 1,2 is. Under our experimental conditions, the yield of ketones 1 and 2 reached 92.0% and 88.0% (in Table 1), respectively. Figure 1’ shows theIR spectra of ketones 1 and 2, in which the strong band emerging at 3462 cm1 assigned to the vibration ofv (OH) of alcohol 1 (at 3471 cm1 for alcohol 2) disappears totally, and a new strong band reappears at near 1750 cm1attributed to C=O vibration of ketone 1 (at 1748 cm1 for ketone 2). In the1H NMR peak at 2.18 ppm assigned to –OH proton of alcohol 1 disappears, and one new 13C NMR peak reappears at 196.90 ppm assigned to the carbon signal of C=O. Similarly, the 1H NMR peak at 2.17 ppm of alcohol 2 cannot be observed in the NMR spectra of ketone 2, and one new 13C NMR peak emerges at 197.52 ppm attributed to the carbon signal of C=O. The above results show the efficient oxidation from =CH–OH to =C=O radical by PCC and the structure of ketones as depicted in Scheme 1’.
Table 1’. Isolated yields of alcohols and ketones
Sample / Catalyst / Alcohol yield (%) / Ketone yield (%)1 / HClO4 / 67.2 / 92
1 / H2SO4 / 80.0 / 92
2 / HClO4 / 40.1 / 88
2 / H2SO4 / 65.5 / 88
Figure 1’. IR spectra of fructose, alcohols 1,2, and ketones 1,2: afructose, b alcohol 1, calcohol 2, dketone 1, eketone 2.
Scheme 1’. Synthetic routes of alcohols1,2 and ketones1,2
1