20034-71-3Relevant articles and documents
Improved selectivity in the chloromethylation of alkylbenzenes in the presence of quaternary ammonium salts
Selva,Trotta,Tundo
, p. 1003 - 1004 (1991)
Improved yield and selectivity in the chloromethylation of aromatic hydrocarbons in the presence of several phase transfer catalysts are reported. The best yield (98%) and selectivity (p/o ratio = 8.2) were obtained in the chloromethylation of cumene in the presence of a classical micellar catalyst.
A fully integrated high-throughput screening methodology for the discovery of new polyolefin catalysts: Discovery of a new class of high temperature single-site group (IV) copolymerization catalysts
Boussie, Thomas R.,Diamond, Gary M.,Goh, Christopher,Hall, Keith A.,LaPointe, Anne M.,Leclerc, Margarete,Lund, Cheryl,Murphy, Vince,Shoemaker, James A. W.,Tracht, Ursula,Turner, Howard,Zhang, Jessica,Uno, Tetsuo,Rosen, Robert K.,Stevens, James C.
, p. 4306 - 4317 (2007/10/03)
For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH2Ph)4 (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [η2- (N,O)-(2-MeO-C6H4) (2,4,6-Me3C6H2)N]Hf (CH2Ph)3 (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein.
Photochemistry of Cyclopropene Derivatives. 20. Deuterium Isotope Effects in the Triplet-Induced Photochemistry of Tetrasubstituted Cyclopropenes
Padwa, Albert,Chou, Chuen S.,Rosenthal, Robert J.,Rubin, Byron
, p. 3057 - 3068 (2007/10/02)
The photochemical behavior of a number of 3-(o-alkylphenyl)-substituted cyclopropenes which contain a benzylic hydrogen in the γ-position of the side chain has been studied in mechanistic detail.The results obtained indicate that the products of the direct and triplet-sensitized photolysis are completely different.The singlet states of these systems react by ?-bond cleavage of the ring to give products which are explicable in terms of the chemistry of vinyl carbenes.The triplet state, generated by sensitization techniques, undergoes hydrogen atom abstraction by mechanism analoqous to the well-known Norrish type II process of carbonyl compounds.Rate constants for hydrogen abstraction were obtained by plotting Φo/Φq vs. trans-stilbene at a constant quencher to cyclopropene ratio.In contrast to the symmetrically substituted 1,2-diphenylcyclopropenes, the quantum efficiency of hydrogen abstraction of the 1,3 isomers was found to depend on the concentration of starting material.The primary deuterium isotope effect encountered with the symmetrical 1,2-diphenylcyclopropene systems is significantly larger than any previously reported value for hydrogen transfer to an excited state (kH/kD ca. 20/1).A substantial tunnel effect is proposed to rationalize the results.In contrast to the results obtained with the symmetrical cyclopropenes, a much smaller effect on the quantum efficiency was observed with the unsymmetrical systems (kH/kD = 3.3/1).
