596-43-0Relevant articles and documents
C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple
Bower, Jamey K.,Cypcar, Andrew D.,Henriquez, Brenda,Stieber, S. Chantal E.,Zhang, Shiyu
supporting information, p. 8514 - 8521 (2020/05/28)
Despite the growing interest in the synthesis of fluorinated organic compounds, few reactions are able to incorporate fluoride ions directly into alkyl C-H bonds. Here, we report the C(sp3)-H fluorination reactivity of a formally copper(III) fluoride complex. The C-H fluorination intermediate, LCuF, along with its chloride and bromide analogues, LCuCl and LCuBr, were prepared directly from halide sources with a chemical oxidant and fully characterized with single-crystal X-ray diffraction, X-ray absorption spectroscopy, UV-vis spectroscopy, and 1H nuclear magnetic resonance spectroscopy. Quantum chemical calculations reveal significant halide radical character for all complexes, suggesting their ability to initiate and terminate a C(sp3)-H halogenation sequence by sequential hydrogen atom abstraction (HAA) and radical capture. The capability of HAA by the formally copper(III) halide complexes was explored with 9,10-dihydroanthracene, revealing that LCuF exhibits rates 2 orders of magnitude higher than LCuCl and LCuBr. In contrast, all three complexes efficiently capture carbon radicals to afford C(sp3)-halogen bonds. Mechanistic investigation of radical capture with a triphenylmethyl radical revealed that LCuF proceeds through a concerted mechanism, while LCuCl and LCuBr follow a stepwise electron transfer-halide transfer pathway. The capability of LCuF to perform both hydrogen atom abstraction and radical capture was leveraged to enable fluorination of allylic and benzylic C-H bonds and α-C-H bonds of ethers at room temperature.
'Redox-switch' catalysis of C-C bond formation with H2: One-electron reduction of the trityl cation
Hembre,McQueen
, p. 65 - 67 (2007/10/03)
Different products are formed from the electron transfer reaction between the ruthenium hydride 1 and the trityl cation when 1 is employed as a 'redox-switch' catalyst or as stoichiometric reducing agent. In the first case 1 converts H2 into a one-electron reducing agent for C-C bond formation, thus yielding the product known as Gomberg's dimer. In contrast, only triphenylmethane is produced in the stoichiometric reactions, by an electron-transfer/hydride-transfer mechanism.
EQUILIBRIUM CONSTANTS FOR TRIPHENYLMETHYL BROMIDE AND 3-BROMO-3-PHENYLDIIRINE IN ACETONITRILE
Liu, Michael T. H.,Paike, N.
, p. 3763 - 3766 (2007/10/02)
The equilibrium constatns at 25 deg C are 7.6E-3 and 2.0E-5 for triphenylmethyl bromide and bromidazirine respectively.
Triphenylmethyl Phenylcyanomethylenenitronate: Formation and Thermolysis
Boyer, Joseph H.,Manimaran, Thankiavelu,Ramakrishnan, Vayalakkavoor T.
, p. 2163 - 2170 (2007/10/02)
The previously reported formation of carbon dioxide, α,α'-bis(tritylazo)stilbene (4), benzonitrile N-oxide (5), trityl isocyanate (6), and C33H25N3O (11) from a mixture ot trityl chloride and silver phenylcyanomethylenenitronate in toluene is now attributed to the initial formation at -20 deg C of trityl phenylcyanomethylenenitronate (3) and its dissociations at 5 deg C.The ester (3) was characterized by conversion into bromonitrophenylacetonitrile (7) by treatment with bromine, to p-nitrobenzoyl cyanide (8) by treatment with dinitrogen tetraoxide, to trityl alcohol by hydrolysis, and to a mixture of trityl alcohol and trityl peroxide by exposure to the atmosphere.The bisazostilbene (4) (18percent) and C33H25N3O, identified by X-ray crystallographic analysis to be 4,5-diphenyl-1-triphenylmethoxy-1,2,3-triazole (11) (24percent), were obtained from the nitronate ester (3) in toluene at 5 deg C; the nitrile oxide (5) and the isocyanate (6) were obtained in low yields from the ester (3) in dimethyl sulphoxide at 25 deg C.Hydrolysis converted the triazole (11) into 1-hydroxy-4,5-diphenyl-1,2,3-triazole (12) and trityl alcohol.Silver p-bromophenylcyanomethylenenitronate and trityl chloride afforded α,α'-bis-(tritylazo)-p,p'-dibromostilbene and its thermolysis product, p,p'-dibromodiphenylacetylene.Fragmentation of the ester (3) in presence of added phenyl isocyanate gave the bisazo compound (4) and 3,4-diphenyl-1,2,4-oxodiazol-5-one (18).A similar mixture stored at -20 deg C gave the triazole (11) and the oxadiazolone (18).Aroyl nitrile oxides as well as phenyl isocyanate suppressed the formation of the red bisazostilbene (4).The intermediacy of the N-trityl imine (14) of 4H-3-phenyl-1,2-oxazet-4-one-2-oxide in the thermolysis of the nitronate (3) was discussed.
Electrophilic Reactivity of the Triphenylmethyl Carbocation in Aqueous Solutions
McClelland, Robert A.,Banait, Narinder,Steenken, Steen
, p. 7023 - 7027 (2007/10/02)
The triphenylmethyl (trityl) carbocation has been generated as a transient intermediate by laser flash photolysis of 1:2 (v/v) acetonitrile:water solutions of trityl acetate and trityl 4-cyanophenyl ether.Identification of the transient as the free carbocation in the ground state was based on its characteristic absorption spectrum and upon conductivity changes.Rate constants have been measured for the reaction of the cation in this solvent with a series of ionic and neutral nucleophiles.The solvent rate constant at 20 deg C is 1.5 x 105 s-1.Azide ions reacts at 4.1 x 109 M-1s-1; the directly measured azide:water ratio is compared to literature values determined by product analysis.Chloride ion reacts at 2 x 106 M-1 s-1; with bromide the equilibrium addition can be observed with k(comb) = 5 x 106 M-1 s-1 and k(ion) for Ph3CBr = 8 x 105 s-1.Rate constants do not adhere to the N+ relationship.This predicts a slope of unity in a plot of log k(Ph3C+) vs.N+, with the better nucleophiles reacting at the 1010 encounter-controlled limit.Azide is the only nucleophile of those studied to approach this.Sulfite and thiolate ions, which are better N+ nucleophiles, react at 2-3 x 108 M-1s-1, while amines react in the 106-107 M-1s-1 range.The plot vs.N+ has a slope of 0.3-0.4.One explanation is that rate constants for the better nucleophiles do level, but this occurs considerably below the 1010 limit.Alternatively, the less than unit slope is real and this more reactive cation, in contrast to more stable analogues, is exhibiting selectivity.
Antibiotics and derivatives thereof having β-lactamase inhibitory activity and production thereof
-
, (2008/06/13)
A novel antibiotic substance of the formula STR1 wherein R1 is CH3 and R2 is --CH2 --CH2 -- or R1 is H and R2 is --CH=CH--; and R3 represents hydrogen, lower alkyl or triphenylmethyl, and including the salts of the compound of formula (I) wherein R3 is hydrogen, said antibiotic substance having strong antibiotic activity and β-lactamase inhibiting effect, and a method for producing the same by aerobic cultivation of Streptomyces A271.
Ionisation of Triphenylmethylbromide in Nitromethane
Heublein, Guenther,Bauerfeind, Dietmar
, p. 882 - 886 (2007/10/02)
Dissolving triphenylmethylbromide in nitromethane leads to the formation of HBr which complicates conductivity and spectroscopic measurements of carbenium ion absorption.As a result of addition of bromide ions (as tetraethylammonium bromide = Et4NBr) the triphenylmethylabsorption totally disappeares.It can be concluded that Ph3CBr in nitromethane is partially present in form of free (solvated) ions.The carbenium ion concentration has been determined as a function of gross concentration and temperature.
