13865-57-1Relevant academic research and scientific papers
Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki-Miyaura Reactions of Diarylmethyl Esters
Dardir, Amira H.,Casademont-Reig, Irene,Balcells, David,Ellefsen, Jonathan D.,Espinosa, Matthew R.,Hazari, Nilay,Smith, Nicholas E.
, p. 2332 - 2344 (2021/06/28)
The synthesis of triarylmethanes via Pd-catalyzed Suzuki-Miyaura reactions between diarylmethyl 2,3,4,5,6-pentafluorobenzoates and aryl boronic acids is described. The system operates under mild conditions and has a broad substrate scope, including the coupling of diphenylmethanol derivatives that do not contain extended aromatic substituents. This is significant as these substrates, which result in the types of triarylmethane products that are prevalent in pharmaceuticals, have not previously been compatible with systems for diarylmethyl ester coupling. Furthermore, the reaction can be performed stereospecifically to generate stereoinverted products. On the basis of DFT calculations, it is proposed that the oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrate occurs via an SN2 pathway, which results in the inverted products. Mechanistic studies indicate that oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrates to (IPr)Pd(0) results in the selective cleavage of the O-C(benzyl) bond in part because of a stabilizing η3-interaction between the benzyl ligand and Pd. This is in contrast to previously described Pd-catalyzed Suzuki-Miyaura reactions involving phenyl esters, which involve selective cleavage of the C(acyl)-O bond, because there is no stabilizing η3-interaction. It is anticipated that this fundamental knowledge will aid the development of new catalytic systems, which use esters as electrophiles in cross-coupling reactions.
Organocatalytic friedel-crafts benzylation of heteroaromatic and aromatic compounds via an SN1 pathway
Watanabe, Naruhisa,Matsugi, Aoi,Nakano, Keiji,Ichikawa, Yoshiyasu,Kotsuki, Hiyoshizo
supporting information, p. 438 - 442 (2014/03/21)
The Friedel-Crafts-type benzylation of various π-excessive heteroaromatic and aromatic compounds with trityl or benzhydryl halides was efficiently promoted by a thiourea catalyst. This is a novel example of thiourea catalysis of aromatic alkylation by way
Di- and triarylmethylium ions as probes for the ambident reactivities of carbanions derived from 5-benzylated Meldrum's acid
Chen, Xi,Tan, Yue,Berionni, Guillaume,Ofial, Armin R.,Mayr, Herbert
, p. 11069 - 11077 (2014/10/15)
The kinetics of the reactions of carbocations with carbanions 1 derived from 5-benzyl-substituted Meldrum's acids 1-H (Meldrum's acid=2,2-dimethyl-1,3- dioxane-4,6-dione) were investigated by UV/Vis spectroscopic methods. Benzhydryl cations Ar2CH+ added exclusively to C-5 of the Meldrum's acid moiety. As the second-order rate constants (kC) of these reactions in DMSO followed the linear free-energy relationship lg k=s N(N+E), the nucleophile-specific reactivity parameters N and s N for the carbanions 1 could be determined. In contrast, trityl cations Ar3C+ reacted differently. While tritylium ions of low electrophilicity (E-2) reacted with 1 through rate-determining β-hydride abstraction, more Lewis acidic tritylium ions initially reacted at the carbonyl oxygen of 1 to form trityl enolates, which subsequently reionized and eventually yielded triarylmethanes and 5-benzylidene Meldrum's acids by hydride transfer.
Modular synthesis of triarylmethanes through palladium-catalyzed sequential arylation of methyl phenyl sulfone
Nambo, Masakazu,Crudden, Cathleen M.
supporting information, p. 742 - 746 (2014/01/23)
Triarylmethanes, which are valuable structures in materials, sensing and pharmaceuticals, have been synthesized starting from methyl phenyl sulfone as an inexpensive and readily available template. The three aryl groups were installed through two sequential palladium-catalyzed C-H arylation reactions, followed by an arylative desulfonation. This method provides a new synthetic approach to multisubstituted triarylmethanes using readily available haloarenes and aryl boronic acids, and is also valuable for the preparation of unexplored triarylmethane-based materials and pharmaceuticals. Unsymmetric triarylmethanes have been synthesized starting from methyl phenyl sulfone as an inexpensive and readily available template. The three aryl groups were installed through two sequential palladium-catalyzed C-H arylation reactions, followed by an arylative desulfonation. Copyright
Additive effects on palladium-catalyzed deprotonative-cross-coupling processes (DCCP) of sp3 C-H bonds in diarylmethanes
Bellomo, Ana,Zhang, Jiadi,Trongsiriwat, Nisalak,Walsh, Patrick J.
, p. 849 - 857 (2013/03/28)
Palladium-catalyzed cross-coupling reactions have become one of the most useful tools in modern organic chemistry. Current methods to achieve direct functionalization of sp3 C-H bonds of arenes and heteroarenes often employ substrates with appropriately placed directing groups to enable reactivity. Examples of intermolecular arylation methods of weakly acidic sp3 C-H bonds in the absence of directing groups, however, are still limited. We describe herein a study on the use of additives in Pd-catalyzed deprotonative-cross-coupling processes (DCCP) of sp3 C-H bonds of diarylmethanes with aryl bromides at room temperature. These studies resulted in development of four new efficient Pd-catalyzed DCCP using additives that enabled the generation of a range of sterically and electronically diverse aryl- and heteroaryl containing triarylmethanes in good to excellent yields. Additive identification and optimization of all reaction conditions (additive loading, solvent and temperature) were performed using high-throughput experimentation (HTE). The approach outlined herein is expected to be generalizable to other C-H functionalization reactions involving the deprotonation of weakly acidic C-H bonds. The Royal Society of Chemistry 2013.
Towards a comprehensive hydride donor ability scale
Horn, Markus,Schappele, Ludwig H.,Lang-Wittkowski, Gabriele,Mayr, Herbert,Ofial, Armin R.
supporting information, p. 249 - 263 (2013/02/25)
Rates of hydride transfer from several hydride donors to benzhydrylium ions have been measured at 20 °C and used for the determination of empirical nucleophilicity parameters N and sN according to the linear free energy relationship log k20 °C=sN(N+E). Comparison of the rate constants of hydride abstraction by tritylium ions with those calculated from the reactivity parameters sN, N, and E showed fair agreement. Therefore, it was possible to convert the large number of literature data on hydride abstraction by tritylium ions into N and sN parameters for the corresponding hydride donors, and construct a reactivity scale for hydride donors covering more than 20 orders of magnitude.
Palladium-catalyzed C(sp3)-H arylation of diarylmethanes at room temperature: Synthesis of triarylmethanes via deprotonative-cross-coupling processes
Zhang, Jiadi,Bellomo, Ana,Creamer, Andrea D.,Dreher, Spencer D.,Walsh, Patrick J.
supporting information; experimental part, p. 13765 - 13772 (2012/10/08)
Although metal-catalyzed direct arylation reactions of non- or weakly acidic C-H bonds have recently received much attention, chemists have relied heavily on substrates with appropriately placed directing groups to steer reactivity. To date, examples of intermolecular arylation of unactivated C(sp3)-H bonds in the absence of a directing group remain scarce. We report herein the first general, high-yielding, and scalable method for palladium-catalyzed C(sp3)-H arylation of simple diarylmethane derivatives with aryl bromides at room temperature. This method facilitates access to a variety of sterically and electronically diverse hetero- and nonheteroaryl-containing triarylmethanes, a class of compounds with various applications and interesting biological activity. Key to the success of this approach is an in situ metalation of the substrate via C-H deprotonation under catalytic cross-coupling conditions, which is referred to as a deprotonative-cross-coupling process (DCCP). Base and catalyst identification were performed by high-throughput experimentation (HTE) and led to a unique base/catalyst combination [KN(SiMe3)2/Pd-NiXantphos] that proved to efficiently promote the room-temperature DCCP of diarylmethanes. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of substrates that are known to undergo O-, N-, enolate-, and C(sp2)-H arylation.
Mechanism of the photodissociation of 4-diphenyl(trimethylsilyl)methyl- N,N-dimethylaniline
Tasis, Dimitrios A.,Siskos, Michael G.,Zarkadis, Antonios K.,Steenken, Steen,Pistolis, Georgios
, p. 4274 - 4280 (2007/10/03)
On irradiation in hexane (248- and 308-nm laser light) 4- diphenyl(trimethylsilyl)methyl-N,N- dimethylaniline, 2, undergoes photodissociation of the C-Si bond giving 4-N,N-dimethylaminotriphenylmethyl radical, 3(·) (λ(max) at 343 and 403 nm), in very high quantum yield (Φ = 0.92). The intervention of the triplet state of 2 (λ(max) at 515 nm) is clearly demonstrated through quenching experiments with 2,3-dimethylbuta-1,3- diene, styrene, and methyl methacrylate using nanosecond laser flash photolysis (LFP). The formation of 3(·) is further demonstrated using EPR spectroscopy. The detection of the S1 state of 2 was achieved using 266-nm picosecond LFP, and its lifetime was found to be 1400 ps, in agreement with the fluorescence lifetime (τ(f) = 1500 ps, Φ(f)= 0.085). The S1 state is converted almost exclusively to the T1 state (Φ(T) = 0.92). In polar solvents such as MeCN, 2 undergoes (1) photoionization to its radical cation 2(·)+, and (2) photodissociation of the C-Si bond, giving radical 3(·) as before in hexane. The formation of 2(·)+ occurs through a two-photon process. Radical cation 2(·)+ does not fragment further, as would be expected, to 3(·) via a nucleophile(MeCN)-assisted C-Si bond cleavage but regenerates the parent compound 2. Obviously, the bulkiness of the triphenylmethyl group prevents interaction of 2(·)+ with the solvent (MeCN) and transfer to it of the electrofugal group Me3Si+. The above results of the laser flash photolysis are supported by pulse radiolysis, fluorescence measurements, and product analysis.
Synthesis and characterization of 4'-amino and 4'-nitro derivatives of 4-N,N-dimethylaminotriphenylmethane as precursors for a proximate malachite green metabolite
Cho, Bongsup P,Blankenship, Lonnie R,Moody, Joanna D,Doerge, Daniel R,Beland, Frederick A,Culp, Sandra J
, p. 7379 - 7388 (2007/10/03)
This paper describes the preparation of 4'-amino (2) and 4'-nitro (3) derivatives of 4-N,N-dimethylaminotriphenylmethane as precursors for presumed DNA-binding metabolites of malachite green. The primary amine 2 was synthesized via a condensation of 4-lit
