[reaction: see text] The reaction of a variety of indoles with N-thioalkyl- and N-thioarylphthalimides to produce 3-thioindoles is reported. Catalytic quantities of halide-containing salts are crucial to the success of this reaction. This highly efficient reaction provides sulfenylated indoles from bench-stable, readily available starting materials in good to excellent yields.
General. NMR spectra were recorded with a Bruker DPX 300, AV 400, or DMX 600 spectrometer in the solvents indicated; chemical shifts (δ) are given in ppm relative to TMS, coupling constants (J) in Hertz. The solvent signals were used as references and the chemical shifts converted to the TMS scale (CDCl 3 : δ C = 77.0 ppm; residual CHCl 3 in CDCl 3 : δ H = 7.24 ppm; CD 2 Cl 2 : δ C = 53.8 ppm; residual CH 2 Cl 2 in CD 2 Cl 2 : δ H = 5.32 ppm). Where indicated, the signal assignments are unambiguous; the numbering scheme is arbitrary and is shown in the inserts. The assignments are based upon 1D and 2D spectra recorded using the following pulse sequences from the Bruker standard pulse program library: DEPT; COSY (cosygs and Negishi carboalumination: Preparation of vinyl iodide 25.A solution of AlMe 3 (2.0 M in heptane, 21.2 mL, 42.4 mmol) was added to a suspension of Cp 2 ZrCl 2 (4.64 g, 15.9 mmol) in 1,2-dichloroethane (70 mL). After stirring for 0.5 h, a solution of alkyne 24 (3.56 g, 10.57 mmol) in 1,2-dichloroethane (15 mL) was added dropwise. The resulting yellow solution was stirred for 24 h at ambient temperature before the mixture was cooled to −20°C and a solution of iodine (16.10 g, 63.5 mmol) in THF (60 mL) was slowly added. After stirring for 20 min at −20°C and 30 min at 0°C, the reaction was carefully quenched with water (10 mL). A sat. aq. Na 2 SO 3 solution was then added and the layers were separated. The aqueous phase was extracted twice with CH 2 Cl 2 (40 mL each), the combined organic extracts were washed with brine, dried over MgSO 4 and evaporated. .7, 135.7, 134.0, 129.7, 127.8, 75.4, 61.8, 39.9, 37.7, 27.0, 20.5, 19.6, 19.3 was added dropwise to a solution of epoxide 7 (7.6 g, 30.84 mmol) in toluene (25 mL) at −78°C over the course of 1 h. The temperature was then raised to −40°C and stirring continued for 4 h before the reaction was carefully quenched at −60°C with a solution of tBuOH in THF (1:1, 25 mL). The resulting mixture was poured into an icecold solution of Rochelle's salt (85g in 250 mL water) and vigorously stirred for 2 h until a clear separation of the phases was reached. The aqueous layer was extracted with tert-butyl methyl ether, the combined organic phases were dried over Na 2 SO 4 and evaporated, and the residue was purified by flash chromatography (hexanes:EtOAc, 1:1) to give product 8 as a
General. NMR spectra were recorded with a Bruker DPX 300, AV 400, or DMX 600 spectrometer in the solvents indicated; chemical shifts (δ) are given in ppm relative to TMS, coupling constants (J) in Hertz. The solvent signals were used as references and the chemical shifts converted to the TMS scale (CDCl 3 : δ C = 77.0 ppm; residual CHCl 3 in CDCl 3 : δ H = 7.24 ppm; CD 2 Cl 2 : δ C = 53.8 ppm; residual CH 2 Cl 2 in CD 2 Cl 2 : δ H = 5.32 ppm). Where indicated, the signal assignments are unambiguous; the numbering scheme is arbitrary and is shown in the inserts. The assignments are based upon 1D and 2D spectra recorded using the following pulse sequences from the Bruker standard pulse program library: DEPT; COSY (cosygs and Negishi carboalumination: Preparation of vinyl iodide 25.A solution of AlMe 3 (2.0 M in heptane, 21.2 mL, 42.4 mmol) was added to a suspension of Cp 2 ZrCl 2 (4.64 g, 15.9 mmol) in 1,2-dichloroethane (70 mL). After stirring for 0.5 h, a solution of alkyne 24 (3.56 g, 10.57 mmol) in 1,2-dichloroethane (15 mL) was added dropwise. The resulting yellow solution was stirred for 24 h at ambient temperature before the mixture was cooled to −20°C and a solution of iodine (16.10 g, 63.5 mmol) in THF (60 mL) was slowly added. After stirring for 20 min at −20°C and 30 min at 0°C, the reaction was carefully quenched with water (10 mL). A sat. aq. Na 2 SO 3 solution was then added and the layers were separated. The aqueous phase was extracted twice with CH 2 Cl 2 (40 mL each), the combined organic extracts were washed with brine, dried over MgSO 4 and evaporated. .7, 135.7, 134.0, 129.7, 127.8, 75.4, 61.8, 39.9, 37.7, 27.0, 20.5, 19.6, 19.3 was added dropwise to a solution of epoxide 7 (7.6 g, 30.84 mmol) in toluene (25 mL) at −78°C over the course of 1 h. The temperature was then raised to −40°C and stirring continued for 4 h before the reaction was carefully quenched at −60°C with a solution of tBuOH in THF (1:1, 25 mL). The resulting mixture was poured into an icecold solution of Rochelle's salt (85g in 250 mL water) and vigorously stirred for 2 h until a clear separation of the phases was reached. The aqueous layer was extracted with tert-butyl methyl ether, the combined organic phases were dried over Na 2 SO 4 and evaporated, and the residue was purified by flash chromatography (hexanes:EtOAc, 1:1) to give product 8 as a
We investigated a formation channel of triatomic molecular hydrogen ions from ethane dication induced by irradiation of intense laser fields (800 nm, 100 fs, ∼1 × 10(14) W∕cm(2)) by using time of flight mass spectrometry. Hydrogen ion and molecular hydrogen ion (H,D)(n)(+) (n = 1-3) ejected from ethane dications, produced by double ionization of three types of samples, CH(3)CH(3), CD(3)CD(3), and CH(3)CD(3), were measured. All fragments were found to comprise components with a kinetic energy of ∼3.5 eV originating from a two-body Coulomb explosion of ethane dications. Based on the signal intensities and the anisotropy of the ejection direction with respect to the laser polarization direction, the branching ratios, H(+):D(+) = 66:34, H(2)(+):HD(+):D(2)(+) = 63:6:31, and H(3)(+):H(2)D(+):HD(2)(+):D(3)(+) = 26:31:34:9 for the decomposition of C(2)H(3)D(3)(2+), were determined. The ratio of hydrogen molecules, H(2):HD:D(2) = 31:48:21, was also estimated from the signal intensities of the counter ion C(2)(H,D)(4)(2+). The similarity in the extent of H∕D mixture in (H,D)(3)(+) with that of (H,D)(2) suggests that these two dissociation channels have a common precursor with the C(2)H(4)(2+)...H(2) complex structure, as proposed theoretically in the case of H(3)(+) ejection from allene dication [A. M. Mebel and A. D. Bandrauk, J. Chem. Phys. 129, 224311 (2008)]. In contrast, the (H,D)(2)(+) ejection path with a lower extent of H∕D mixture and a large anisotropy is expected to proceed essentially via a different path with a much rapid decomposition rate. For the Coulomb explosion path of C-C bond breaking, the yield ratios of two channels, CH(3)CD(3)(2+)→ CH(3)(+) + CD(3)(+) and CH(2)D(+) + CHD(2)(+), were 81:19 and 92:8 for the perpendicular and parallel directions, respectively. This indicates that the process occurs at a rapid rate, which is comparable to hydrogen migration through the C-C bond, resulting in smaller anisotropy for the latter channel that needs H∕D exchange.
A general approach to the regio- and stereoselective total synthesis of the benanomicin-pradimicin antibiotics (BpAs) is described. Construction of the aglycon has been achieved by 1) the diastereoselective ring-opening of a biaryl lactone by using (R)-valinol as a chiral nucleophile and 2) the stereocontrolled semi-pinacol cyclization of the aldehyde acetal by using SmI(2) in the presence of BF(3)OEt(2) and a proton source to afford the ABCD tetracyclic monoprotected diol. This strategy enabled us to control the two stereogenic sites in the B ring (C-5 and C-6) and the regioselective introduction of the carbohydrate moiety. The ABCD tetracycle could serve as an ideal platform for the divergent access to various BpAs. The amino acid (D-alanine) was introduced onto the ABCD tetracycle. Glycosylation was promoted by the combination of Cp(2)HfCl(2) and AgOTf (1:2 ratio). Construction of the E ring followed by deprotection completed the first total synthesis of benanomicin A (2 a), benanomicin B (2 b), and pradimicin A (1 a). The route is flexible enough to allow the synthesis of other congeners differing in their amino acid and carbohydrate moieties.
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