89321-49-3Relevant academic research and scientific papers
Picosecond radical kinetics. Rate constants for ring openings of 2-aryl-substituted cyclopropylcarbinyl radicals
Newcomb,Choi,Toy
, p. 1123 - 1135 (2007/10/03)
The kinetics of ring openings of a series of eight (trans-2-arylcyclopropyl)methyl radicals (1) were studied by indirect kinetic methods using Barton's PTOC esters as radical precursors and reaction with PhSeH as the competition reaction. The substituents were CF3, F, Me, and OMe located on both the para and meta positions of the aromatic ring. Syntheses of the radical precursors and the products of the radical reactions are described. Kinetics were determined between -43 and 25°C in four cases (CF3 and OMe substituents) and at 0 and 25°C in the other four cases. The rate constants at 25°C ranged from 1.0 x 1011 s-1 (p-CH3) to 4.1 x 1011 s-1 (p-CF3). The relatively large acceleration of the p-CF3 group, ca. 2.5 times as fast as the parent system with Ar = Ph, correlates well with Adam's ΔD substituent parameters but not with other radical substituent parameters. These calibrated radical rearrangements provide a new set of ultrafast reactions that can be applied in mechanistic probe studies.
A Substituted Hypersensitive Radical Probe for Enzyme-Catalyzed Hydroxylations: Synthesis of Racemic and Enantiomerically Enriched Forms and Application in a Cytochrome P450-Catalyzed Oxidation
Toy, Patrick H.,Dhanabalasingam, Bhavani,Newcomb, Martin,Hanna, Imad H.,Hollenberg, Paul F.
, p. 9114 - 9122 (2007/10/03)
The syntheses of racemic and enantiomerically enriched trans-1-methyl-2-(4-(trifluoromethyl)phenyl)cyclopropane (3) and the possible oxidation products from enzyme-catalyzed hydroxylation of 3 at the methyl group are reported. The important intermediate in the production of 3 was the Weinreb amide of the 2-arylcyclopropanecarboxylic acid which could be prepared in diastereomerically pure form and which also served as an intermediate for production of the cyclic oxidation products of 3. Hydroxylation of 3 by the cytochrome P450 isozyme CYP2B1 gave cyclic and ring-opened products. The product ratios support an insertion mechanism for the enzyme-catalyzed hydroxylation reaction in which minor amounts of rearranged products are produced by radical fragmentation within the transition structure of the insertion and by a competing reaction involving a cationic species. Formation of cationic rearrangement products by a heterolytic fragmentation reaction of a first-formed protonated alcohol product is suggested on the basis of the apparent amounts of cationic products formed in the hydroxylation of 3. This pathway for cation production appears to require that the activated enzyme complex (equivalent to enzyme-substrate-H2O2) oxidizes substrate before water dissociates to give an iron-oxo species.
Synthesis and spectral characterization of a series of iron and ruthenium benzylidene complexes, Cp(CO)(L)M=CH(C6H4R)+ (M = Fe, Ru; L = CO, PPh3; R = p-H, p-F, p-CH3, p-OCH3). Barriers to a
Brookhart,Studabaker, William B.,Humphrey, M. Beth,Husk, G. Ronald
, p. 132 - 140 (2008/10/08)
The α-ether complexes Cp(CO)2Fe-CH(OCH3)C6H4R (7a, R = H; 7b, R = p-F; 7c, R = p-CH3; 7d, R = p-OCH3; 7e, R = m-OCH3; 7f, R = p-CF3), Cp(CO)2Ru-CH(OCH3
