4237-08-5Relevant academic research and scientific papers
Palladium-catalyzed hydrophenylation of bicyclic alkenes
Mayo, Peter,Tam, William
, p. 9527 - 9540 (2002)
Palladium-catalyzed hydrophenylation reactions of bicyclic alkenes were investigated. These reactions were found to be completely chemo- and stereoselective, giving only exo products on the less substituted double bonds of bicyclic alkenes in moderate to good yields. For unsymmetrical bicyclic alkenes, regioselectivities of 52:48 to 100:0 were observed with various substituents on the bicyclic alkenes.
Carbocation-forming reactions in dimethyl sulfoxide
Creary, Xavier,Burtch, Elizabeth A.,Jiang, Ziqi
, p. 1117 - 1127 (2007/10/03)
Mesylate derivatives of 3-aryl-3-hydroxy-β-lactams and thiolactams react in DMSO-d6 by first-order processes to give alcohol products. Substituent effect studies implicate carbocation intermediates (ion-pairs) that are captured by DMSO-d6 to give transient oxosulfonium ions. Rapid reaction of the oxosulfonium ions with trace amounts of water leads to the alcohol product and regenerates DMSO-d6. H217O labeling studies show that 17O is incorporated into the DMSO. The mesylate derivatives of endo- and exo-2-hydroxy-2-phenylbicyclo[2.2.1]heptan-3-one also react in DMSO-d6 to give the alcohol products. Ion-pair intermediates that capture DMSO giving unstable oxosulfonium ions are again proposed. Exo-2-phenyl-endo-bicyclo[2.2.1]heptyl trifluoroacetate readily eliminates trifluoroacetic acid in DMSO-d6 via a cationic mechanism involving loss of the endotrifluoroacetate leaving group as well as an exo-hydrogen. The O-methyl oxime derivative of α-chloroα,α-diphenylacetophenone reacts in DMSO-d6 to give 1-methoxy-2,3-diphenylindole, a product derived from cyclization of a cationic intermediate. A common ion rate suppression provides further evidence for a cationic mechanism. The triflate derivative of pivaloin reacts by a cationic mechanism in DMSO-d6 to give rearranged products. The rate is even faster than in highly ionizing solvents such as trifluoroethanol or trifluoroacetic acid. 1-Adamantyl mesylate reacts in DMSO-d6 by a first-order process (YOMs = -4.00) to give a long-lived oxosulfonium ion, 1-Ad-OS(CD3)2+, which can be characterized spectroscopically. This oxosulfonium ion reacts only slowly with water at elevated temperatures to give 1-adamantanol. DMSO is therefore a viable solvent for ks, kC, and kΔ cationic processes.
Solvolytic elimination reactions. Stepwise or concerted?
Creary, Xavier,Casingal, Vincent P.,Leahy, Charlene E.
, p. 1734 - 1738 (2007/10/02)
2-Aryl-endo-2-norbornyl trifluoroacetates 11 solvolyze to give a significant fraction of elimination product. A deuterium labeling study showed that the exo hydrogen is lost exclusively when the elimination product forms. A concerted ester pyrolysis type of mechanism is therefore ruled out. The tertiary benzylic trifluoroacetate Ph(CH3)C(CONMe2)(OCOCF3), 12, solvolyzes to give exclusively an elimination product. The β-CD3 isotope effect on rate was 1.15. There is, however, a larger isotope effect (2.5) in formation of the elimination product when Ph(CH2D)C(CONMe2)(OCOCF3) solvolyzes. The mechanism therefore has a minimum of two steps since the product-determining step and the rate-determining step have differing isotope effects. A concerted elimination mechanism is ruled out. The ortho-dimethyl-substituted cumyl trifluoroacetate 13 also solvolyzes to give an elimination product. The β-D6 isotope effect of 1.61 is in the "normal" range for a secondary isotope effect in a carbocation-forming reaction. This argues against a concerted elimination mechanism. These results contrast with the recent suggestion that cumyl systems give elimination product via a concerted elimination mechanism. The analogous tertiary benzylic systems 11-13 all give solvolytic elimination products via discrete cationic intermediates.
Changing selectivity in palladium-catalyzed reactions involving oxidation state IV. A new synthesis from iodobenzene and norbornene
Catellani, Marta,Chiusoli, Gian Paolo,Castagnoli, Carlo
, p. C30 - C33 (2007/10/02)
The formation of organopalladium intermediates in a catalytic reaction between iodobenzene and norbornene, involving a palladium(0)-(II)-(IV)-(II)-(0) sequence, can be directed towards preferential formation of product V or IV.
A NEW PALLADIUM-CATALYZED SYNTHESIS OF 1,2,3,4,4a,8b-HEXAHYDRO-1,4-METHANOBIPHENYLENES AND 2-PHENYLBICYCLOHEPT-2-ENES
Catellani, Marta,Chiusoli, Gian Paolo,Ricotti, Stefano
, p. C11 - C16 (2007/10/02)
Aromatic bromides react with bicyclohept-2-ene in the presence of palladium(0) coplexes and alkali phenoxides to give hexahydromethanobiphenylenes and phenylbicycloheptenes, probably via palladacyclic intermediates.Use of hindered phenoxides leads to selective cyclobutene ring closure.
PALLADIUM-CATALYZED C-C BOND FORMATION INVOLVING AROMATIC C-H ACTIVATION. IV. NEW SYNTHETIC APPLICATIONS OF INSERTION REACTIONS COUPLED WITH INTRAMOLECULAR AROMATIC SUBSTITUTION
Catellani, Marta,Chiusoli, Gian Paolo,Ricotti, Stefano,Sabini, Fabrizio
, p. 685 - 690 (2007/10/02)
Synthetic potentialites of new types of Pd-catalyzed intramolecular aromatic substitution, involving strained olefin insertion, have been explored.The reaction leading to hexahydromethanobiphenylene derivatives in their exo form appears to offer the widest synthetic applications.The use of hindered phenoxides is shown to lead to high selectivity.
Electrophilic Aromatic Substitution. Part 30. The Effects of the p-Bicyclooctan-1-yl, Adamantan-1-yl, exo-and endo-Norbornan-2-yl,and Neopentyl Substituents in Detritiation. Steric Acceleration of Hyperconjugation
Archer, William J.,Morteza, A. Hossaini,Taylor, Roger
, p. 181 - 186 (2007/10/02)
Rate coefficients have been measured for detritiation of compounds (p-3H)C6H4R by anhydrous trifluoracetic acid at 70 deg C, and lead to the following partial rate factors(R=): bicyclooctan-1-yl, 2650; adamantan-1-yl, 2000; exo-norbornan-2-yl, 175
