Synthesis and reactions of a cyclopentadienylidene ketene complex (original) (raw)
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J. Org.Chem. 1982, 47, 2055-2060.pdf
h. 1BF NMR analysis (standard C&,CFJ showed that cycloadduct 15 was formed in 63% yield (cis,truns-15/truns,truns-l5 ratio of 83/17). The reaction mixture was submitted to methanolysis in a manner similar to that for the desilylation of 14.
Supplementary Information Chem. Commun. 2012 D'Errico et al
All the reagents were obtained from commercial sources (Sigma-Aldrich) and were used without further purification. 1 H and 13 C-NMR spectra were acquired on a Varian Mercury Plus 400 MHz and on a Varian Unit Inova 700 MHz in CD 3 OD or CDCl 3 . Chemical shifts are reported in parts per million (δ) relative to the residual solvent signals: CD 2 HOD 3.31 and CHCl 3 7.27 for 1 H-NMR; CD 2 HOD 49.0 and CHCl 3 77.0 for 13 C-NMR. 1 H-NMR chemical shifts were assigned by 2D NMR experiments. The abbreviations s, bs, d, dd and m stand for singlet, broad singlet, doublet, doublet of doublets and multiplet, respectively. HPLC analyses and purifications were carried out on a Jasco UP-2075 Plus pump equipped with a Jasco UV-2075 Plus UV detector using a 4.60 x 150 mm LUNA (Phenomenex) silica column (particle size 5 µm) eluted with a linear gradient of MeOH in AcOEt (from 0 to 5% in 15 min, flow 1.0 mL min -1 , system A), with a linear gradient of AcOEt in n-hexane (from 0 to 100% in 30 min, flow 1.0 mL min -1 , system B) or using a 4.8 x 150 mm C-18 reverse-phase column (particle size 5 µm) eluted with a linear gradient of MeOH in H 2 O (from 0 to 100% in 30 min, flow 1.3 mL min -1 , system C). UV spectra were recorded on a Jasco V-530 UV spectrophotometer. High Resolution MS spectra were recorded on a Bruker APEX II FT-ICR mass spectrometer using electrospray ionization (ESI) technique in positive mode. Elemental analyses were performed on a Thermo Finnigan Flash EA 1112 CHN analyser. IR spectra were recorded on a Jasco FT-IR 430 spectrophotometer. Optical rotations were determined on a Jasco polarimeter using a 1 dm cell at 25 °C; concentrations are in g/100 mL. Preparative PLC chromatography was performed using F254 silica gel plates (0.5 mm thick, Merck). Analytical TLC analyses were performed using F254 silica gel plates (0.2 mm thick, Merck). TLC spots were detected under UV light (254 nm). For MTS assays the UV absorbance at 490 nm was read using a Beckman Anthos 96 well Microplate Reader.
The Journal of Organic Chemistry, 1992
To a stirred and cooled (-100 OC) solution of 4 (40 mg, 0.32 mmol) in THF (4 mL) was added via cannula a cooled (-100 OC) LDA solution prepared from i-PrzNH (49 pL, 0.34 mmol) and BuLi (1.48 M in hexane, 0.22 mL, 0.33 mmol) in THF (1.5 mL). After 8 min, dry DMPU (77 pL, 0.64 "01) was introduced, and to the mixture was added a solution of 63 (63 mg, 0.107 "01) in THF (1.5 mL) over a 2-min period.
Journal of Organic Chemistry, 1989
t) ppm. (lE,3E)-l-Phenyl-4-(phenylthi0)-1,3,5-hexatriene (7k) was prepared on a 0.50-mmol scale from tram-cinnamaldehyde in 83% yield. The triene was found to be unstable and polymerized on standing at room temperature and was not fully characterized: Rf0.25 (1% ether/petroleum ether); 'H NMR (CDCl,, 300 MHz) 6 7. 18-7.46 (m, 11 H), 6.99 (dd, J = 16.5, 10.5 Hz, 1 H), 6.58-6.98 (m, 2 H), 7.75 (d, J = 16.5 Hz, 1 H), 5.33 (dt, J = 10.5, 1.5 Hz, 1 H) ppm; 13C NMR (CDCl,, 75 MHz) 6 136.87 (s), 136.48 (d), 135.50 (s), 135.16 (d), 132.72 (s), 130.53 (d), 129.70 (d), 128.90 (d), 128.65 (d), 128.09 (d), 126.67 (d), 126.34 (d), 123.30 (d), 118.99 (t) ppm.
J. Am.Chem.Soc. 1988, 110, 3247-3252.pdf
Acid-catalyzed rearrangement of 6-bromo-2,4-dimethyl-4-(phenylamino)cyclohexa-1 ,4-dienone (1, a quinamine) in aqueous methanol gives, from a so-called quinamine rearrangement, 4'-amino-6-bromo-2,4-dimethyldiphenyl ether (2) and a number of byproducts. The ratio of yield of 2 to that of byproducts is 76:24. The byproducts are, mostly, 1,3-dimethylcarbazole (7) and some of its derivatives, the relative yields of which depend on the concentration of the catalyzing acid, HCI. The major byproduct in low HC1 concentrations is 1,3-dimethyl-4-methoxycarbazole (9). Kinetic isotope effects (KIE) were measured for the formation of 2 from 1, which was labeled at the carbonyl oxygen atom (['*0]-1), the nitrogen atom ([I5N]-1), and the para position of the aniline ring ([4-I4C]-1). The KIE (averages) were as follows: k ( ' 6 0 ) / k ( 1 8 0 ) , 1.0399; k(I4N)/k(l5N), 1.0089; /~( ' * c ) / k (~~C ) , 1.0501. The results suggest that the formation of 2 is a concerted process, a [5,5]-sigmatropic rearrangement, and not a two-step one, going through the rate-determining formation of a r-complex. KIE were measured for the formation of both 2 and 9 from 1, which was labeled in the ortho position of the anilino ring ([2-14C]-1). The KIE [k(12C)/k(14C)] were respectively 0.9895 and 1.0697. These results suggest that the byproduct (9) is formed by a concerted process, too, a [3,3]-sigmatropic rearrangement to an intermediate , which continues on to 9 and the other byproducts. The results show also that 2 cannot be formed from 1 by a succession of two [3,3]-sigmatropic rearrangements, the first of which is to 14. Thus, the quinamine rearrangements. on the basis of our results with 1, appear to be concerted, rather than a-complex intermediate, processes.