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31.
Biswanath Das Katta Venkateswarlu Maddeboina Krishnaiah Harish Holla Anjoy Majhi 《Helvetica chimica acta》2006,89(7):1417-1421
Treatment of Baylis–Hillman adducts 1 with bromo(dimethyl)sulfonium bromide, Br(Me2)S+Br?, in MeCN was found to stereoselectively afford (Z)‐ and (E)‐allyl bromides 2 . The reaction is rapid at room temperature, high‐yielding, and highly stereoselective. 相似文献
32.
Described is the construction of a furanyl-cylcobutanone fragment suited for incorporation into a synthesis of the naturally occurring anti-cancer agent Providencin. 相似文献
33.
Crystal Structures of [Et3PNAsPh3]2[Ag2Br4] and [Et3PNAsPh3]2[Pd2Br6] Colourless single crystals of [Et3PNAsPh3]2[Ag2Br4]( 1 ) and red single crystals of [Et3PNAsPh3]2[Pd2Br6]( 2 ) have been isolated from saturated solutions in acetonitrile of equivalent mixtures of [Et3PNAsPh3]Br with AgBr and PdBr2, respectively. Both complexes were characterized by IR spectroscopy and by crystal structure determinations. 1 : Space group P1¯, Z = 1, lattice dimensions at ‐70°C: a = 985.0(2), b = 1042.2(5), c = 1345.8(5) pm, α = 102.88(2)°, β = 105.73(2)°, γ = 94.94(2)°, R1 = 0.0577. 2 : Space group P21/c, Z = 2, lattice dimension at ‐70°C: a = 1003.0(1), b = 1371.8(2), c = 1974.0(1) pm, β = 93.30(1)°, R1 = 0.0458. The dimeric anions of 1 and 2 form planar, centrosymmetric complex units. 相似文献
34.
Treatment of Pd(PPh3)4 with 2‐bromo‐4‐methylpyridine, C5H3N(CH3)Br, in dichloromethane at ?20 °C causes the oxidative addition reaction to produce the palladium complex [Pd(PPh3)2 {η1‐C5H3N(CH3)}(Br)], 2 , by substituting two triphenylphosphine ligands. In a dichloromethane solution of complex 2 at room temperature for 3 h, it undergoes displacement of the triphenylphosphine ligand to form the dipalladium complex [Pd(PPh3)Br]2{μ,η2‐C5H3N(CH3)}2, 3 , in which the two 4‐methylpyridine ligands coordinated through carbon to one metal center and bridging the other metal through the nitrogen atom. Complexes 2 and 3 are characterized by X‐ray diffraction analyses. 相似文献
35.
The hexamethylenetetramine/trifluoroacetic acid system was demonstrated to be capable of introducing three aldehyde groups into the phenol molecule. Facile, one-step procedures were developed for the preparation of hitherto difficult to synthesize 2-hydroxy-1,3,5-benzenetricarbaldehyde starting from either phenol or 4-hydroxybenzaldehyde. New pKa measurements showed 2-hydroxy-1,3,5-benzenetricarbaldehyde to be an acid stronger than previously reported. 相似文献
36.
The first report on the use of N-sulfinyl benzylcarbamate for the preparation of N-Cbz sulfilimine from the corresponding sulfoxide is reported. The sulfilimine moiety is utilized as an intramolecular nucleophile for the regio- and stereoselective heterofunctionalization of an alkene to furnish a bromo carbamate which is used as a key advanced intermediate in the synthesis of representative α-hydroxy-β-amino acid derivatives. 相似文献
37.
Sulagna Brahma 《Tetrahedron letters》2005,46(38):6575-6578
A simple and useful method for the synthesis of azirines containing an aldehyde functionality, from open chain bromo/chloro-aldehydes at room temperature and their stabilization as palladium(II) complexes are reported. 相似文献
38.
Jorgelina L. Pergomet Teodoro S. Kaufman Andrea B. J. Bracca 《Helvetica chimica acta》2016,99(5):398-404
A straightforward approach toward 6‐bromo‐2‐isopropylidenecoumaranone, a potential intermediate toward alkaloid TMC 120‐B, pseudodeflectusin, and other natural products, was reported. The synthetic sequence involved the reaction of 3‐bromosalicylaldehyde with chloroacetone and cyclization of the resulting ether to a 2‐acetylcoumaranol intermediate. This was followed by sequential methyl Grignard addition and Jones’ oxidation to the corresponding coumaranone, which was dehydrated to the final product with the methanesulfonyl chloride/pyridine reagent. The protection of the coumaranol as the corresponding THP‐ether resulted in improved product yields. 相似文献
39.
Summary A reversed-phase high performance liquid chromatographic method on C-18 bonded silica is described for the separation of trisubstituted iodo/bromothyronines, which exert thyroid hormone activity. The composition of the mobile phase has been systematically optimized resulting in a ternary mixture of methanol/acetonitrile/water acidified with trifluoroacetic acid. The applicability of ultraviolet absorption detection, amperometric detection and off-line radioimmunoassay was investigated. The latter method allows detection of the different iodo/bromothyronines down to 40–120 ng/l mobile phase; this sensitivity is high enough for application to thyroid hydrolysates in order to clarify the question as to whether bromine can substitute iodine in the biosynthesis of thyroid hormones. 相似文献