- Niobium Pentachloride Mediated (Hetero)aromatic Aldehyde Friedel-Crafts Hydroxyalkylation with Arenes: An Efficient Strategy to Synthesize Triarylmethanes
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Niobium pentachloride is an efficient and useful Lewis acid to conduct Friedel-Crafts hydroxyalkylation between arenes and (hetero)aromatic aldehydes, to generate triarylmethanes. This practical methodology offers several advantages, such as short reaction time, mild experimental conditions, and excellent yields.
- Baviera, Giovanni S.,Donate, Paulo M.,Matias, Alexandre A.,Previdi, Daniel,Rodrigues, Shirley M. M.
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p. 4498 - 4506
(2019/11/21)
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- Lewis acid-mediated mono- and bis-addition of C-nucleophiles to 1,3-dioxolan-4-ones
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The reactions of 1,3-dioxolan-4-ones, readily available from α-hydroxy acids and aldehydes, with C-nucleophiles are described. Two possible reaction pathways resulting in O-substituted acids and tri-(hetero)arylmethanes are shown.
- Shcherbinin, Vitaly A.,Konshin, Valery V.
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p. 3005 - 3009
(2018/07/06)
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- Solventless triarylmethane synthesis via hydroxyalkylation of anisole with benzaldehyde by modified heteropoly acid on mesocellular foam silica (MCF)
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Triarylmethane (TRAM) compounds have wide applications such as leuco dyes for sensing tumors and other biological activities. Hydroxyalkylation of arenes with benzaldehyde results in formation of triarylmethane compounds. In the present study, 20 (wt.%) Cs2.5H0.5PW12O40 (Cs-DTP) supported on mesocellular foam (MCF) silica was prepared, characterized and tested for its activity in hydroxyalkylation reaction of anisole with benzaldehyde. Its activity was compared with commercial catalysts like Amberlyst-15, montmorillonite clay K-10, H3PW12O40 and unsupported Cs2.5H0.5PW12O40.The prepared catalyst showed the best activity compared to others with advantage of separation of catalyst and reusability. Reaction parameters were studied in detail and kinetic study was carried out for the said reaction. 20 (wt. %) Cs-DTP/MCF was found to be the best, robust and reusable catalyst. Reaction mechanism and kinetics were also studied. The results are new.
- Bhadra, Kalpesh H.,Yadav, Ganapati D.
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p. 150 - 158
(2018/06/18)
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- Synthesis of Tetraarylmethanes by the Triflic Acid-Promoted Formal Cross-Dehydrogenative Coupling of Triarylmethanes with Arenes
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The formal cross-dehydrogenative coupling of triarylmethanes with arenes promoted by triflic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is described. This method provides a variety of tetraarylmethane derivatives in good to excellent yields from triarylmethanes that can be readily prepared by our previous methods. Control experiments suggest a possible catalytic cycle involving the generation of a trityl cation intermediate followed by nucleophilic addition of the arene.
- Nambo, Masakazu,Yim, Jacky C.-H.,Fowler, Kevin G.,Crudden, Cathleen M.
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supporting information
p. 2936 - 2940
(2017/10/09)
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- Triggering the approach of an arene or heteroarene towards an aldehyde via Lewis acid-aldehyde communication
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The present work reports a combined experimental/computational study of the Lewis acid promoted hydroxyalkylation reaction involving aldehyde and arene/heteroarene and reveals a mechanism in which the rate determining aldehyde to alcohol formation via a four-member cyclic transition state (TS) involves a transfer of hydrogen from arene/heteroarene C-H to aldehyde oxygen with the breaking of the C-H bond and formation of C-C and O-H bonds. The effect of different Sn(iv) derivatives on the hydroxyalkylation reaction from different in situ NMR and computational studies reveals that although the exergonic formation of the intermediate and its gained electrophilicity at the carbonyl carbon drive the reaction in SnCl4 compared to other Sn(iv) derivatives, the overall reaction is low yielding because of its stable intermediate. With respect to different aldehydes, LA promoted hydroxylation was found to be more feasible for an electron withdrawing aldehyde compared to electron rich aldehyde because of lower stability, enhanced electrophilicity gained at the aldehyde center, and a lower activation barrier between its intermediate and TS in the former as compared to the latter. The relative stability of the LA-aldehyde adduct decreases in the order SnCl4 > AlCl3 > InCl3 > BF3 > ZnCl2 > TiCl4 > SiCl4, while the activation barrier (ΔG#) between intermediate and transition states increases in the order AlCl3 4 3 3 4 2 4. On the other hand, the activation barriers in the case of different arenes/heteroarenes are in the order of indole 3, InCl3 and SnCl4 because they have negative free energy of formation (ΔG) for alcohol to the corresponding diaryl methyl carbocation.
- Pratihar, Sanjay
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p. 2854 - 2865
(2016/03/12)
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- Hydride Reduction by a Sodium Hydride-Iodide Composite
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Sodium hydride (NaH) is widely used as a Br?nsted base in chemical synthesis and reacts with various Br?nsted acids, whereas it rarely behaves as a reducing reagent through delivery of the hydride to polar π electrophiles. This study presents a series of reduction reactions of nitriles, amides, and imines as enabled by NaH in the presence of LiI or NaI. This remarkably simple protocol endows NaH with unprecedented and unique hydride-donor chemical reactivity.
- Too, Pei Chui,Chan, Guo Hao,Tnay, Ya Lin,Hirao, Hajime,Chiba, Shunsuke
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p. 3719 - 3723
(2016/03/26)
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- Friedel-crafts alkylation of arenes catalyzed by ion-exchange resin nanoparticles: An expedient synthesis of triarylmethanes
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Friedel-Crafts alkylation of electron-rich arenes with aldehydes has been achieved in the presence of an active and selective Amberlyst-15 catalyst at the reaction temperature of 60 ° C in solvent-free conditions. The catalyst exhibitsby a very high activity and offers the corresponding triarylmethanes in excellent yields with a high selectivity. The use of highly reactive and selective Amberlyist-15 makes this procedure simple, convenient, cost-effective, practical and environmentally friendly. This method provides an easy access to triarylmethanes in a single step using a readily available acidic ionic resin, which is a stable and easy to separate from the reaction mixture by a simple filtration technique.
- Reddy, B. V. Subba,Venkateswarlu,Sridevi,Aldeyab, Salem S.,Vinu, Ajayan
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p. 6826 - 6832
(2015/11/24)
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- The cooperative effect of Lewis pairs in the Friedel-Crafts hydroxyalkylation reaction: A simple and effective route for the synthesis of (±)-carbinoxamine
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An efficient C-C bond formation strategy between aromatic/heteroaromatic π-nucleophiles and Lewis acid activated aldehydes is described. This aromatic electrophilic substitution reaction of arenes or heteroarenes is facilitated by Lewis acid AlBr3. Aromatic rings with electron donating substituents are excellent nucleophilic counterparts in this reaction, generating carbinols in excellent yields (61-94%). The formation of triarylmethanes is also witnessed in the case of certain reactive aldehydes and aromatic π-nucleophiles through reactive carbocation formation. The formation of triarylmethane is reduced to a greater extent via retardation of the second π-nucleophile addition through a Lewis base, for example, pyridine, coordination with an aluminium alkoxide intermediate. Various aliphatic aldehydes also underwent Friedel-Crafts type hydroxyalkylation and generated the expected carbinols in moderate yields (41-53%) in the presence of AlBr3. This protocol has been successfully applied to the synthesize of the (±)-carbinoxamine, a therapeutically important histamine H1 antagonist, in a one-pot manner.
- Harikrishnan, Adhikesavan,Sanjeevi, Jayakumar,Ramanathan, Chinnasamy Ramaraj
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p. 3633 - 3647
(2015/03/30)
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- Iron-catalyzed arylation of aromatic ketones and aldehydes mediated by organosilanes
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A simple and efficient iron-catalyzed method for arylation of aromatic carbonyl compounds is reported. The use of 4-% FeCl3 or Fe(acac) 3 as the catalyst, in combination with a slight excess of chlorotrimethylsilane and triethylsilane, chlorination of benzylic ketones and aldehydes with subsequent Friedel-Crafts alkylation of arenes is achieved. Although the method is limited by the general constraints associated with Friedel-Crafts alkylation reactions, robust applications for the synthesis of pharmaceutical intermediates and so on can be envisioned. A robust one-pot, iron-catalyzed chlorination Friedel-Crafts alkylation reaction of benzylic carbonyl compounds, mediated by chlorotrimethylsilane and triethylsilane, has been developed to yield substituted diaryl and triaryl building blocks. Copyright
- Savela, Risto,Majewski, Marcin,Leino, Reko
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p. 4137 - 4147
(2014/07/08)
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- Di- and triarylmethylium ions as probes for the ambident reactivities of carbanions derived from 5-benzylated Meldrum's acid
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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.
- Chen, Xi,Tan, Yue,Berionni, Guillaume,Ofial, Armin R.,Mayr, Herbert
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p. 11069 - 11077
(2014/10/15)
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- Room-temperature bismuth-catalyzed bis-arylation of carbonyl compounds with aryl ethers and phenols
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Using Bi2(SO4)3 as the catalyst and TMSCl as the additive, a wide variety of aldehydes, ketones, and acetals were smoothly condensed with aryl ethers at room temperature to provide the corresponding diarylmethanes and triarylmethanes selectively in good to excellent yields. Using Bi2(SO4)3 as the catalyst and TMSCl as the additive, a wide variety of aldehydes, ketones, and acetals were smoothly condensed with aryl ethers at room temperature to selectively provide the corresponding diarylmethanes and triarylmethanes in good to excellent yields. Copyright
- Liu, Congrong,Li, Manbo
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supporting information
p. 1274 - 1278
(2013/11/06)
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- Towards a comprehensive hydride donor ability scale
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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.
- Horn, Markus,Schappele, Ludwig H.,Lang-Wittkowski, Gabriele,Mayr, Herbert,Ofial, Armin R.
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supporting information
p. 249 - 263
(2013/02/25)
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- Friedel-Crafts hydroxyalkylation through activation of a carbonyl group using AlBr3: An easy access to pyridyl aryl/heteroaryl carbinols
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Aromatic electrophilic substitution of aromatic/electron rich heteroaromatic compounds with AlBr3 activated aldehydes/ketone to afford pyridyl aryl/heteroaryl or diaryl carbinols is described. The strong electron donating group dictates the regiochemical outcome of the product.
- Harikrishnan, Adhikesavan,Selvakumar, Jayaraman,Gnanamani, Elumalai,Bhattacharya, Suman,Ramanathan, Chinnasamy Ramaraj
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supporting information
p. 563 - 567
(2013/04/10)
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- Additive effects on palladium-catalyzed deprotonative-cross-coupling processes (DCCP) of sp3 C-H bonds in diarylmethanes
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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.
- Bellomo, Ana,Zhang, Jiadi,Trongsiriwat, Nisalak,Walsh, Patrick J.
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p. 849 - 857
(2013/03/28)
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- Friedel-crafts arylation reactions of N -sulfonyl aldimines or sulfonamidesulfones with electron-rich arenes catalyzed by FeCl 3·6H2O: Synthesis of triarylmethanes and bis-heteroarylarylmethanes
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(Figure presented) The FeCl3·6H2O-catalyzed Friedel-Crafts arylation reactions of N-sulfonyl aldimines or sulfonamidesulfones with electron-rich arenes and heteroarenes, which lead to the formation of triarylmethanes and bis-heteroar
- Thirupathi, Ponnaboina,Soo Kim, Sung
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experimental part
p. 5240 - 5249
(2010/10/03)
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- Preparation of triaryl- and triheteroarylmethanes under ytterbium triflate catalysis and solvent-free conditions
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Triaryl- and triheteroarylmethanes have been synthesized in very good yield under solvent-free conditions from differently substituted aldehydes and 2-methylfuran or methoxybenzene in the presence of Yb(OTf)3 as catalyst. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Genovese, Salvatore,Epifano, Francesco,Pelucchini, Caroline,Curini, Massimo
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experimental part
p. 1132 - 1135
(2009/06/18)
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- Versatile friedel-crafts-type alkylation of benzene derivatives using a molybdenum complex/ortho-chloranil catalytic system
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A variety of molybdenum complexes catalyze Friedel-Crafts-type alkylation reactions of benzene derivatives with alkenes and alcohols in the presence of an organic oxidant, o-chloranil. The utilization of [Mo(CO)6] and two equivalents of o-chloranil catalytically furnished the hydroarylation product of norbornene with p-xylene at 80°C, whereas [Cr(CO)6] and [W(CO)6] failed to catalyze the same reaction, thus indicating the importance of the molybdenum source. The best results were obtained when a molybdenum(II) complex [CpMoCl(CO)3] (Cp = cyclopentadienyl) was used as a precatalyst. The hydroarylation reactions also took place with styrenes, cyclohexenes, and 1 -hexene as olefin substrates. The electrophilic-substitution mechanism was proposed on the basis of the ortho/para selectivities and the Markovnikov selectivities observed for the hydroarylation products. Our hypothesis was further corroborated by the fact that in the presence of the [CpMoCl(CO)3]/o-chloranil catalytic system, secondary, benzylic, or allylic alcohols participated in the alkylation of benzenes with similar selectivities.
- Yamamoto, Yoshihiko,Itonaga, Kouhei
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experimental part
p. 10705 - 10715
(2009/12/01)
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- Catalytic selective bis-arylation of imines with anisole, phenol, thioanisole and analogues
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The first highly efficient double Friedel-Crafts reaction of N-tosyl imines with anisole, phenol, thioanisole and analogues has been developed to produce the corresponding symmetric diarylmethanes and triarylmethanes with high regioselectivity in the presence of a catalytic amount of Bi2(SO 4)3-TMSCl at room temperature. The Royal Society of Chemistry.
- Liu, Cong-Rong,Li, Man-Bo,Yang, Cui-Feng,Tian, Shi-Kai
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p. 1249 - 1251
(2008/12/21)
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- Convenient synthesis of triarylmethanes and 9,10-diarylanthracenes by alkylation of arenes with aromatic aldehydes using acetyl bromide and ZnBr2/SiO2
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Reaction of electron-rich arenes with acetyl bromide and aldehydes in the presence of silica gel-supported zinc bromide was carried out in benzene to give selectively the corresponding triarylmethanes or 9,10-diarylanthracenes in high yields depending upon the ratio of an arene and an aldehyde. The mild conditions employed are especially noteworthy.
- Kodomari, Mitsuo,Nagamatsu, Maki,Akaike, Megumi,Aoyama, Tadashi
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p. 2537 - 2540
(2008/09/21)
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- Dual-reagent catalysis within Ir-Sn domain: Highly selective alkylation of arenes and heteroarenes with aromatic aldehydes
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(Chemical Equation Presented) Reactions of arenes and heteroarenes with aromatic aldehydes proceeded smoothly in the presence of a catalytic combination of [Ir(COD)Cl]2-SnCl4 to afford the corresponding triarylmethane derivatives (TRAMs) in high yields. This 100% TRAM selective transformation is clean and eliminates the use of acid systems.
- Podder, Susmita,Choudhury, Joyanta,Roy, Ujjal Kanti,Roy, Sujit
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p. 3100 - 3103
(2008/02/05)
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- METHOD FOR ESTABLISHING CC BONDS BETWEEN ELECTROPHILIC SUBSTRATES AND ? - NUCLEOPHILES IN NEUTRAL TO ALKALINE AQUEOUS OR ALCOHOLIC SOLVENTS WITHOUT USING A LEWIS OR BRONSTED ACID
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The invention relates to a method for establishing carbon-carbon bonds by reacting electropohilic substrates that have a solvolysis rate kEtOH (25°C) > 10-6 s-1 and ? compounds. The method is characterized by generating the intermediary carbocations in neutral to alkaline aqueous or alcoholic solvents or solvent mixtures without using a Lewis or Br?nsted acid.
- -
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Page/Page column 18-19
(2008/06/13)
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- A convenient method for the synthesis of 4,4-diarylbut-1-enes via the successive allylation of aromatic aldehydes and the Friedel-Crafts alkylation reaction of aromatic nucleophiles with the intermediary benzyl silyl ethers using HfCl4 or Cl2Si(OTf)2
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The three-component coupling reaction among aromatic aldehydes, allyltrimethylsilane and aromatic nucleophiles is efficiently performed by the promotion of HfCl4. A similar reaction occurs using allyltributyltin as the first nucleophile to aromatic aldehydes with a catalytic amount of Cl2Si(OTf)2 generated in situ from SiCl4 and AgOTf.
- Shiina, Isamu,Suzuki, Masahiko,Yokoyama, Kazutoshi
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p. 6395 - 6398
(2007/10/03)
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- Novel stereoselective control over cis vs trans opening of benzo[c]phenanthrene 3,4-diol 1,2-epoxides by the exocyclic N2-amino group of deoxyguanosine in the presence of hexafluoropropan-2-ol
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We describe a novel and efficient synthesis (62-84% yields) of the eight possible, diastereomerically pure, cis and trans, R and S O6-allyl-protected N2-dGuo phosphoramidite building blocks derived through cis and trans opening of (±)-3α,4β-dihydroxy-1β,2β-epoxy-1,2,3, 4-tetrahydrobenzo[c]-phenanthrene [BcPh DE-1 (1)] and (±)-3α,4β-dihydroxy-1α,2α-epoxy-1,2,3, 4-tetrahydrobenzo[c]-phenanthrene [BcPh DE-2 (2)] by hexafluoropropan-2-ol (HFP)-mediated addition of O6-allyl-3′,5′- di-O-(tert-butyldimethylsilyl)-2′-deoxyguanosine (3) at C-1 of the epoxides. Simply changing the relative amount of HFP used in the reaction mixture can achieve a wide ratio of cis/trans addition products. Thus, the observed cis/trans adduct ratio for the reaction of DE-1 (1) in the presence of 5 equiv of 3 varied from 17/83 to 91/9 over the range of 5-532 equiv of HFP. The corresponding ratios for DE-2 (2) varied from 2/98 to 61/39 under the same set of conditions. When 1 or 2 was fused with a 20-fold excess of 3 at 140°C in the absence of solvent HFP, almost exclusive trans addition (>95%) was observed for the both DEs. Through the use of varying amounts of HFP in the reaction mixture as described above, each of the eight possible phosphoramidite oligonucleotide building blocks (DE-1/DE-2, cis/trans, R/S) of the BcPh DE N2-dGuo adducts can be prepared in an efficient fashion. To rationalize the varying cis-to-trans ratio, we propose that the addition of 3 to 1 or 2 in the absence of solvent or in the presence of small amounts of HFP proceeds primarily via an SN2 mechanism to produce mainly trans-opened adducts. In contrast, increasing amounts of HFP promote increased participation of an SN1 mechanism involving a relatively stable carbocation with two possible conformations. One of these conformations reacts with 3 to give mostly trans adduct, while the other conformation reacts with 3 to give mostly cis adduct.
- Yagi, Haruhiko,Ramesha, Andagar R.,Kalena, Govind,Sayer, Jane M.,Kumar, Subodh,Jerina, Donald M.
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p. 6678 - 6689
(2007/10/03)
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- Structural requirements for decarbonylative α,α-diarylation reaction of 2-methoxyalkanoic acids in phosphorus pentoxide-methanesulfonic acid mixture yielding 1,1-diarylalkane homologs
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2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P2O5-MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.
- Yonezawa, Noriyuki,Hino, Tetsuo,Tokita, Yoshimi,Matsuda, Kazuhisa,Ikeda, Tomiki
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p. 14287 - 14296
(2007/10/03)
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- Mechanism of reduction of trityl halides by lithium dialkylamide bases
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Trityl chloride (TCl) and bromide are reduced by hindered lithium dialkylamide bases in THF to give predominantly triphenylmethane and a small amount of trityl dimer. Rate constants for the reduction of TCl by lithium diisopropylamide and lithium tert-butylethylamide in THF at -78 ?C have been measured; the reactions are first order in monomeric base and in trityl chloride. Inter- and intramolecular kinetic isotope effect studies employing β-deuterium substituted bases and substituent effect studies coupled with other kinetic information were used to formulate a scheme for the reactions. The reactions proceed by a rapid predissociation of the trityl halide to form an ion pair containing the trityl-THF oxonium cation followed by diffusion controlled electron transfer (ET) from the monomeric form of the base to the trityl-THF oxonium ion. The radical pair thus formed reacts by fast, highly regioselective β-hydrogen atom transfer from the aminyl radical to the methine carbon of the trityl radical to give triphenylmethane. Radical escape from the cage is a minor competing process. An outer-sphere ET process is energetically acceptable, but an inner-sphere process appears to be more likely.
- Newcomb, Martin,Varick, Thomas R.,Goh, Swee-Hock
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p. 5186 - 5193
(2007/10/02)
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- Reactions of some p-Substituted Triphenylmethyl Chlorides with Alcohols, Alkali-metal Alcoholates, and Tributylamine
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The p-methoxylated triphenylmethyl chlorides (4a-c), when heated with alcohols, give mixtures of the corresponding triarylmethanes (5a-c) (via the hydride transfer to the corresponding triarylmethylium cations) and the alkyl (substituted triphenylmethyl) ethers (7a-c) (via polar susbtitution reactions).Part or all of the ether (7c) may be further converted into the substituted triphenylmethanol (6c).In the reaction of the mono-p-methoxylated halides (4a) and (4c) with methanol, the substitution products (7a) and (7c) are formed as the main products, while the main product of the reaction of the di-p-methoxylated halide (4b) with methanol is the substituted triphenylmethane (5b).When the methanol is replaced by 2H4> methanol, no reduction product is formed from the halide (4c).Reaction of halide (4c) with ethanol furnishes exclusively the substituted triphenylmethane (5c).The p-chlorophenyl(diphenyl)methyl chloride (4d) gives, with methanol, mainly or exclusively the ether (7d), and with ethanol, under mild conditions, gives the ether (9d).However, under vigorous conditions, the substituted triphenylmethane (5d) is formed.The reduction of the p-methoxylated triphenylmethyl chloride (4c) by alcohols as well as its conversion into alkyl (p-methoxylated triphenylmethyl) ethers are accompanied, to a certain degree, by exchange of the p-methoxy group of the substrate and the alkoxy group of the alcohol; no similar exchange of the p-chlorine atom of halide (4d) was observed.Explanations for all obsrved diferences are offered.The reactions of the substituted triphenylmethyl chlorides (4b-d) with alkoxides in the corresponding alcohols give the corresponding alkyl (substituted triphenylmethyl) ethers (7b), (7c), (9c), and (9d), respectively, in excellent yields.The reaction of the triarylmethyl chloride (4d) with potassiumt-butoxide in THF in the presence of acetone led, among other products, to the formation of oligomeric material which indicates the operation of single-electron-transfer induced processes.Reaction of the same chloride (4d) with tributylamine in refluxing cumene or t-butylbenzene led to the exclusive formation of a series of products all of which may be derived from the intermediacy of the substituted triphenylmethyl radical (18); the latter, in turn, is thought to arise as a result of dissociative electron transfer from tributylamine to chloride (4d).
- Izso, Gyoengyi,Huszthy, Peter,Lempert, Karoly,Fetter, Jozsef,Simig, Gyula,et al.
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p. 769 - 778
(2007/10/02)
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- NADH Model Studies. Part 2. Cationic Hydrogenations using Acridan Derivatives as Hindered NADH Models.
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Various aryl alcohols (5), arylethylenes (6), and trityl ethers (7) are found to undergo smooth reduction in dichloromethane at room temperature when treated with an equimolar amount of the acridans (3) and trifluoroacetic acid.The limiting acidity value (H0) for the medium in which the compounds (3) are completely protonated and hence not suitable as NADH models was also determined spectrophotometrically.Kinetic studies of reduction of (5) with (3) in dilute sulphuric acid, or Hantzsch ester (2) in glacial acetic acid, indicated that during reduction steric hindrance is important in less acidic media whereas the reduction of cations performed with trifluoroacetic acid is not affected by steric factors.
- Singh, Serjinder,Gill, Sarbjeet,Sharma, Vijay K.,Nagrath, Sarita
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p. 1273 - 1276
(2007/10/02)
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- Cationic Hydrogenation of Benzyl Alcohols and Arylethylenes using Acridane Derivatives as Hindered NADH Models
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Secondary and tertiary benzyl alcohols and arylethylenes are efficiently reduced by acridane derivatives (1) in the presence of trifluoroacetic acid in dichloromethane.
- Singh, Serjinder,Chhina, Sarbjeet,Sharma, Vijay K.,Sachdev, Satbir S.
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p. 453 - 454
(2007/10/02)
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