789-24-2Relevant academic research and scientific papers
Facile synthesis of complicated 9,9-diarylfluorenes based on BF 3·Et2O-mediated Friedel-Crafts reaction
Xie, Ling-Hai,Hou, Xiao-Ya,Hua, Yu-Ran,Tang, Chao,Liu, Feng,Fan, Qu-Li,Huang, Wei
, p. 3701 - 3704 (2006)
BF3·OEt2-mediated Friedel Crafts reaction of 9-phenyl-fluoren-9-ol with electron-rich aromatic substrates to prepare a new family of complicated 9,9-diarylfluorenes is described. The 9,9-diarylfluorenes tethered with various functional substituents, e.g., bulky spiro units, hole-transporting moieties, and fluorescent dyes, will be promising building blocks for the construction of optoelectronic materials.
Decatungstate-Photocatalyzed Radical Addition of 9-Substituted Fluorenes to [60]Fullerene: A Mechanistic Approach
Malliaros, Nikitas G.,Orfanopoulos, Michael
supporting information, p. 4846 - 4850 (2021/09/20)
An innovative, efficient, regioselective functionalization of C60 with 9H-fluorenes has been disclosed. This efficient photochemical approach uses certain fluorenyl radicals in 9-position deriving from fluorenes through a hydrogen-atom transfer (HAT) process mediated by tetrabutylammoniumdecatungstate [(n-Bu4N)4W10O32]. The single addition of these fluorenyl radicals to C60 proceeded to produce [60]fullerene-fluorene dyads in a single step. The scope and mechanism of this new reaction have been examined. The primary kinetic isotope effect measurements signify the presence of a stepwise mechanism in which the C?H (D) bond scission is the rate-limiting step of the reaction.
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.
Transition-Metal-Free Synthesis of Polyfunctional Triarylmethanes and 1,1-Diarylalkanes by Sequential Cross-Coupling of Benzal Diacetates with Organozinc Reagents
Wei, Baosheng,Ren, Qianyi,Bein, Thomas,Knochel, Paul
, p. 10409 - 10414 (2021/03/26)
A variety of functionalized triarylmethane and 1,1-diarylalkane derivatives were prepared via a transition-metal-free, one-pot and two-step procedure, involving the reaction of various benzal diacetates with organozinc reagents. A sequential cross-coupling is enabled by changing the solvent from THF to toluene, and a two-step SN1-type mechanism was proposed and evidenced by experimental studies. The synthetic utility of the method is further demonstrated by the synthesis of several biologically relevant molecules, such as an anti-tuberculosis agent, an anti-breast cancer agent, a precursor of a sphingosine-1-phosphate (S1P) receptor modulator, and a FLAP inhibitor.
The p: K a values of N-aryl imidazolinium salts, their higher homologues, and formamidinium salts in dimethyl sulfoxide
Cole, Marcus L.,Dunn, Michelle H.,Harper, Jason B.,Konstandaras, Nicholas,Luis, Ena T.
supporting information, p. 1910 - 1917 (2020/03/23)
A series of imidazolinium salts, their six-, seven- A nd eight-membered homologues, and the related formamidinium salts were prepared, and their pKa values were determined in DMSO at 25 °C using the bracketing indicator method. The effect of each type of structural variation on the acidity of each salt was considered, particularly noting the importance of ring size and the effect of the steric and electronic nature of the N-aryl substituents. The effect of a cyclic structure was also probed through comparing the cyclic systems with the corresponding formamidinium salts, noting the importance of conformational flexibility in the latter cases. Along with allowing choice of appropriate bases for deprotonation of these species, it is anticipated that the data presented will aid in the understanding of the nucleophilicity, and potentially catalytic efficacy, of the corresponding carbenes.
Mild, Rapid, and Chemoselective Procedure for the Introduction of the 9-Phenyl-9-fluorenyl Protecting Group into Amines, Acids, Alcohols, Sulfonamides, Amides, and Thiols
Soley, Jacob,Taylor, Scott D.
, (2020/02/04)
The 9-phenyl-9-fluorenyl (PhF) group has been used as an Nα protecting group of amino acids and their derivatives mainly as a result of its ability to prevent racemization. However, installing this group using the standard protocol, which employs 9-bromo-9-phenylfluorene/K3PO4/Pb(NO3)2, often takes days and yields can be variable. Here, we demonstrate that the PhF group can be introduced into the amino group of Weinreb's amides and methyl esters of amino acids, as well as into alcohols and carboxylic acids, rapidly and in excellent yields, using 9-chloro-9-phenylfluorene (PhFCl)/N-methylmorpholine (NMM)/AgNO3. Nα-PhF-protected amino acids can be prepared from unprotected α-amino acids, rapidly and often in near quantitative yields, by treatment with N,O-bis(trimethylsilyl)acetamide (BSA) and then PhFCl/NMM/AgNO3. Primary alcohols can be protected with the PhF group in the presence of secondary alcohols in moderate yield. Using PhFCl/AgNO3, a primary alcohol can be protected in good yield in the presence of a primary ammonium salt or a carboxylic acid. Primary sulfonamides and amides can be protected in moderate to good yields using phenylfluorenyl alcohol (PhFOH)/BF3·OEt2/K3PO4, while thiols can be protected in good to excellent yield using PhFOH/BF3·OEt2 even in the presence of a carboxylic acid or primary ammonium group.
Development of a Robust Protocol for the Determination of Weak Acids' p KaValues in DMSO
Jung, Sebastian T.,Podlech, Joachim
, p. 10951 - 10957 (2020/09/23)
Two methods for the determination of pKa values of weak acids are described, a direct titration with dimsyl potassium in the presence of an indicator and a back-titration in which an analyte/indicator mixture is deprotonated and then titrated with ammonium chloride. Both methods have been validated by measuring pKa values of compounds, for which values had been determined previously. The back-titration method was applied to measure pKa values of two 1,3-dithiane-derived bissulfoxides and a monosulfone.
Synthesis, Characterization, and Reactivity of a Hypervalent-Iodine-Based Nitrooxylating Reagent
Calvo, Roxan,Katayev, Dmitry,Le Tellier, Antoine,Nater, Darryl,Nauser, Thomas,Rombach, David
supporting information, p. 17162 - 17168 (2020/07/31)
Herein, the synthesis and characterization of a hypervalent-iodine-based reagent that enables a direct and selective nitrooxylation of enolizable C?H bonds to access a broad array of organic nitrate esters is reported. This compound is bench stable, easy-
Manganese-Catalyzed Synthesis of Quaternary Peroxides: Application in Catalytic Deperoxidation and Rearrangement Reactions
Chaudhari, Moreshwar B.,Gnanaprakasam, Boopathy,Shaikh, Moseen A.,Ubale, Akash S.
, p. 10488 - 10503 (2020/09/23)
Highly efficient, selective, and direct C-H peroxidation of 9-substituted fluorenes has been achieved using a Mn-2,2′-bipyridine catalyst via radical-radical cross-coupling. Moreover, this method effectively promotes the vicinal bisperoxidation of sterically hindered various substituted arylidene-9H-fluorene/arylideneindolin-2-one derivatives to afford highly substituted bisperoxides with high selectivity over the oxidative cleavage of Ca C bond that usually forms the ketone of an aldehyde. Furthermore, a new approach for the synthesis of (Z)-6-benzylidene-6H-benzo[c]chromene has been achieved via an acid-catalyzed skeletal rearrangement of these peroxides. For the first time, unlike O-O bond cleavage, reductive C-O bond cleavage in peroxides using the Pd catalyst and H2 is described, which enables the reversible reaction to afford exclusively deperoxidized products. A detailed mechanism for peroxidation, molecular rearrangement, and deperoxidation has been proposed with preliminary experimental evidences.
Experimental Evidence for p Ka-Driven Asynchronicity in C-H Activation by a Terminal Co(III)-Oxo Complex
Goetz, McKenna K.,Anderson, John S.
, p. 4051 - 4062 (2019/03/07)
C-H activation by transition metal oxo complexes is a fundamental reaction in oxidative chemistry carried out by both biological and synthetic systems. This centrality has motivated efforts to understand the patterns and mechanisms of such reactivity. We have therefore thoroughly examined the C-H activation reactivity of the recently synthesized and characterized late transition metal oxo complex PhB (tBuIm)3CoIIIO. Precise values for the pKa and BDFEO-H of the conjugates of this complex have been experimentally determined and provide insight into the observed reactivity. The activation parameters for the reaction between this complex and 9,10-dihydroanthracene have also been measured and compared to previous literature examples. Evaluation of the rates of reaction of PhB(tBuIm)3CoIIIO with a variety of hydrogen atom donors demonstrates that the reactivity of this complex is dependent on the pKa of the substrate of interest rather than the BDEC-H. This observation runs counter to the commonly cited reactivity paradigm for many other transition metal oxo complexes. Experimental and computational analysis of C-H activation reactions by PhB(tBuIm)3CoIIIO reveals that the transition state for these processes contains significant proton transfer character. Nevertheless, additional experiments strongly suggest that the reaction does not occur via a stepwise process, leading to the conclusion that C-H activation by this CoIII-oxo complex proceeds by a pKa-driven "asynchronous" concerted mechanism. This result supports a new pattern of reactivity that may be applicable to other systems and could result in alternative selectivity for C-H activation reactions mediated by transition metal oxo complexes.
