An acetate anion bearing an imidazolium cation as its charge tag was reacted with M(OAc)(2) complexes (where M = Ni, Cu, and Pd; in situ reaction) to form members of a new class of charge-tagged metal complexes. The formation of these unprecedented precatalysts with potential for cross-coupling reactions was confirmed by electrospray ionization (and tandem) mass spectrometry. The catalytic performance of the palladium complex was tested in Heck and Suzuki cross-coupling reactions, often with superior activity and yields as compared with Pd(OAc)(2).
The /3-carbon of ,/3-unsaturated ketones, esters, lactones, and nitriles can be oxidatively functionalized in a regiospecific manner in a simple sequence of reactions. Michael addition of thiophenol followed by oxidation with jV-chlorosuccinimide gives chloro sulfides that readily lose HC1 to give 3-phenylthio enones, acrylates, and other vinyl derivatives.
The 7-norbornenyl radical is generated in solution by photolysis of syn-and anti-tert-butylperoxy 7-norbornenecarboxylates. Geminate combination of the 7-norbornenyl and tert-butoxy radicals favors antirelative to syn-7-tert-butoxynorbornene from both isomeric peresters. Deuterium labeling at the 7 position indicates that hydrogen abstraction from the solvent also occurs preferentially from the anti side of the norbornenyl radical. The 7-norbornenyl radicals generated from the photolysis of syn or anti perester are, thus, chemically indistinguishable. The esr spectra of the 7-norbornenyl radical and of some deuterium substituted 7-norbornenyl radicals are also reported. The hyperfine isotropic coupling constant for the proton in the 7 position is unusually small (10.8 G) and has a temperature coefficient of opposite sign to those hitherto reported for a protons in alkyl radicals (e.g., methyl). The unusual temperature dependence together with an anomalous isotope shift in the magnitude of the corresponding coupling constant for the deuterium labeled species in the 7 position is consistent with a positice sign for the a-proton coupling constant. INDO-MO calculations support this interpretation and are used in conjunction with the esr data to probe the vibrational behavior and the equilibrium structure in this radical.he 7-norbornenyl system offers a structural frame-
Um catalisador baseado em sílica quimicamente modificada com tetrametilguanidina (TMG) foi sintetizado pela co-condensação de tetraetilortossilicato (TEOS) com um novo agente sililante, preparado pela reação entre a molécula TMG e (3-cloropropil)trimetoxisilano. O direcionador n-dodecilamina foi utilizado para organizar a polimerização do catalisador inorgânico-orgânico. A termogravimetria mostrou que o número de sítios ativos do catalisador foi de 1,35 mmol g .A espectroscopia na região do infravermelho e de ressonância magnética nuclear no estado sólido para os núcleos 29 Si e 13 C confirmou a obtenção do produto desejado. Este material foi usado para catalisar a adição de nitrometano em ciclopentenona. 98% de conversão foi observada depois de 3 h de reação. O catalisador foi recuperado e reutilizado por mais catorze vezes, mantendo uma eficiência catalítica em torno de 98%.A catalyst based on silica chemically modified with tetramethylguanidine (TMG) was synthesized by the co-condensation of tetraethylorthosilicate (TEOS) with a new silylant agent derived from the reaction between the TMG molecule and (3-chloropropyl)trimethoxysilane. A neutral n-dodecylamine template was used to organize the polymerization of the inorganicorganic catalyst. Thermogravimetry showed that the number of active pendant groups in the catalyst was 1.35 mmol g -1 , with a surface area of 811 ± 75 m 2 g -1. Infrared spectroscopy and 13 C and 29 Si nuclear magnetic resonance data are in agreement with the proposed structure. This material has been used to catalyse the addition of nitromethane to cyclopentenone. The catalytic efficiency was followed and the nitromethylcyclopentanone conversion presented a yield of 98% at 3 h of reaction. The catalyst was recovered and reused 14 times, maintaining about 98% of its catalytic efficiency.
ferent time intervals aliquots (4 ml) were withdrawn (under argon) and the resin separated immediately by suction filtration, washed thoroughly with DMF, CH2CI2, and MeOH, and then subjected to amino acid analysis. The rate of decrease in amino acid content was taken as the rate of photolysis of the -methylphenacyl ester anchoring bond. Exactly the same experiments were performed on tetrapeptide resins VII and VIII to determine the rate of photolytic cleavage of the o-nitrobenzyl and benzyl ester linkages. The results are summarized in Figure 1. For the studies of the rates of acidolysis or hydrazinolysis of the resins III, VII, and VIII, 0.5 g each of the samples were stirred individually in 20 volumes each of TFA-CH2CI2 (1:1) or 10% H2NNH2 (DMF) in six separate flasks. Aliquots (1 ml) from each reaction were taken at different times and treated as described above for the photolysis experiments. The results are also shown in Figure 1.
Under controlled conditions and at room temperature, (-)-chrysanthenone (3) and (+)-2,4,4-trimethyl- bicyclo[3.1.1 ]hept-2-en-6-one (11) undergo boron trifluoride catalyzed rearrangement to (+)- 2,6,6-trimethylbicyclo[3.2.0]hept-2-en-7-one (4) and (-)-2,4,4-trimethylbicyclo[3.2.0]hept-2-en-7-one (12), respectively, with high retention of optical activity. On prolonged treatment with the same reagent, (+)-ketone 4 is converted to (-)-2,7,7-trimethylbicyclo[3.2.0]hept-2-en-6-one (8) and the monocyclic compounds (+)-isopiperitenone ( 5), piperitenone (6), and thymol (7). The related exo-chlorobicyclo[3.1.1 jheptanone derivatives 13 and 17 undergo similar stereospecific rearrangement to the corresponding exo-chlorobicyclo[3.2.0]heptanone derivatives 14 and 18, respectively. In order to account for the observed absolute configurations and stereochemistry of products, a
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