- Photochemical Carbene Transfer Reactions of Aryl/Aryl Diazoalkanes—Experiment and Theory**
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Controlling the reactivity of carbene intermediates is a key parameter in the development of selective carbene transfer reactions and is usually achieved by metal complexes via singlet metal-carbene intermediates. In this combined experimental and computational studies, we show that the reactivity of free diaryl carbenes can be controlled by the electronic properties of the substituents without the need of external additives. The introduction of electron-donating and -withdrawing groups results in a significant perturbation of singlet triplet energy splitting of the diaryl carbene intermediate and of activation energies of consecutive carbene transfer reactions. This strategy now overcomes a long-standing paradigm in the reactivity of diaryl carbenes and allows the realization of highly chemoselective carbene transfer reactions with alkynes. We could show that free diaryl carbenes can be readily accessed via photolysis of the corresponding diazo compounds and that these carbenes can undergo highly chemoselective cyclopropenation, cascade, or C?H functionalization reactions. Experimental and theoretical mechanistic analyses confirm the participation of different carbene spin states and rationalize for the observed reactivity.
- Jana, Sripati,Pei, Chao,Empel, Claire,Koenigs, Rene M.
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p. 13271 - 13279
(2021/05/10)
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- The intramolecular reaction of acetophenoneN-tosylhydrazone and vinyl: Br?nsted acid-promoted cationic cyclization toward polysubstituted indenes
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In the presence of TsNHNH2, a Br?nsted acid-promoted intramolecular cyclization ofo-(1-arylvinyl) acetophenone derivatives was developed, leading to polysubstituted indenes with complexity and diversity in moderate to excellent yields. In sharp contrast with either the radical or carbene involved cyclization of aldehydicN-tosylhydrazone with vinyl, a cationic cyclization pathway was involved, whereN-tosylhydrazone served as an electrophile and alkylation reagent during this transformation.
- Wang, Zhixin,Li, Yang,Chen, Fan,Qian, Peng-Cheng,Cheng, Jiang
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p. 1810 - 1813
(2021/02/27)
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- Synthesis of indenes via aluminum chloride-promoted tandem Friedel-Crafts alkylation of arenes and cinnamaldehydes
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A series of substituted indenes were synthesized from arenes and cinnamaldehydes via aluminum chloride-promoted tandem Friedel-Crafts alkylation. The scope and limitation of the tandem reaction were explored. A plausible reaction mechanism is also discuss
- Kheira, Haiouani,Li, Pingfan,Xu, Jiaxi
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p. 168 - 174
(2014/06/09)
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- Reactions of arylacetylenic compounds with arenes in the presence of aluminum halides
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Conjugated arylacetylenic ketones and aldehydes, propargyl-type alcohols, and arylacetylenes reacted with arenes in the presence of AlBr3 or AlCl3 as catalyst to give substituted indenes. 3-Arylpropynoic acids under analogous conditi
- Shchukin,Vasil'Ev,Grinenko
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scheme or table
p. 82 - 97
(2010/06/19)
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- Efficient synthesis of indenes by FeCl3·6H2O-catalyzed intramolecular Friedel-Crafts reaction of aryl-substituted allylic alcohols
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An efficient procedure for the synthesis of substituted indenes through the FeCl3·6H2O-catalyzed intramolecular Friedel-Crafts cyclization of aryl-substituted allylic alcohols has been developed. This method features the easily avail
- Wang, Jialiang,Zhang, Lixin,Jing, Yufeng,Huang, Wen,Zhou, Xigeng
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experimental part
p. 4978 - 4982
(2009/12/01)
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- Friedel-Crafts-type reactions involving di- and tricationic species. Onium-allyl dications and O,O-diprotonated aci-nitro species bearing a protonated carbonyl group
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Stable carbocations do not react with nonactivated benzenes. For example, acetophenone does not react with benzene in the presence of trifluoromethanesulfonic acid (TFSA), while trifluoroacetophenone does do so under acidic conditions owing to activation of the electrophilicity of the hydroxycarbenium cation by the trifluoromethyl group. This and other studies suggest that an electron-withdrawing substituent on the cationic center increases the reactivity toward benzenes. In this paper, involvement of multiply positively charged (dicationic and tricationic) species, which have sufficient electrophilicity toward benzene, is demonstrated in the acid-catalyzed reactions of cinnamaldehyde and its derivatives and also in the acid-catalyzed reactions of nitromethanes. The species formed from cinnamaldehyde, cinnamaldimine, cinnamaldoxime, and their derivatives in TFSA or TFSA-SbF5 have an adequate reactivity toward benzene. O-Protonated cinnamaldehyde and its derivatives, N-protonated cinnamaldimine, and N,N-dimethylcinnamaldiminium salt do not react with benzene. Since a strong acid catalyst is required for the reactions, participation of doubly protonated species, onium-allyl dications, is proposed. Ab initio calculations of (1) the donor-acceptor interaction energies of a neutral donor (such as water and ammonia) and a doubly charged allyl dication and (2) proton affinities demonstrated that the ammonium-allyl dication is more stable than the oxonium-allyl dication, in accordance with the experimental observation. Nitronic acids also react with benzene at the ipso position with respect to the nitro group to give the phenylated oximes in the presence of TFSA. The reaction with benzene is not catalyzed by trifluoroacetic acid, which is sufficiently acidic to monoprotonate a nitronic acid to the protonated aci-nitro form. The reaction requires a stronger acid, trifluoromethanesulfonic acid, suggesting intervention of the dication formed by O,O-diprotonation of acinitroalkanes rather than the monoprotonated aci-nitroalkane. As a result of further study on the phenylation reactions, we found a facile phenylation reaction of nitromethanes substituted with an electron-withdrawing group, catalyzed by TFSA, to give phenylated α-carbonyloximes in high yields. A triply positively charged cation, an O,O-diprotonated aci-nitro species bearing a protonated ethoxycarbonyl group, which can react with nonactivated benzene, is proposed to be an intermediate in this reaction.
- Ohwada, Tomohiko,Yamagata, Naoko,Shudo, Koichi
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p. 1364 - 1373
(2007/10/02)
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- Reactions of α-Oxoketenedithioacetals with Phenylmagnesium Bromide: Synhesis of Novel 1-Phenyl-1-methylthio-3-phenyl (or 2,3-Fused)-indenes and 2,3-Fused Heterocyclic-1,3-Diphenyl-2-alken-1-ones
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Novel substituted and 1-methylthio-1-phenylindenes have been synthesised by boron trifluoride etherate cyclocondensations of the corresponding carbinol acetals obtained by sequential 1,4 and 1,2 additions of phenylmagnesium bromide to α-oxoketenedithioacetals.Some of these indenes have been desulphurized to give the parent ring systems.Synthesis of novel 2,3-fused heterocyclic 1,3-diphenyl-alken-1-ones by boron trifluoride-ether catalyzed methanolysis of the corresponding carbinol acetals has also been described.
- Singh, Gurdeep,Ila, Hiriyakkanawar,Junjappa, Hiriyakkanawar
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p. 744 - 747
(2007/10/02)
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- The SRN1 Photoarylation of Indenyl Anions
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Irradiation of Me2SO solutions of indenyl anion and its phenylated analogues in the presence of bromobenzene produces the higher phenylated indenes.Thus indenyl anion (1b) yields 3-phenylindene (3a), 1-phenylindenyl anion (3b) yields 1,3- and 1,1-diphenylindene, 2-phenylindenyl anion (2b) produces 2,3-diphenylindene, 1,3-diphenylindenyl anion (6b) produces 1,1,3- and 1,2,3-triphenylindene, and 1,2-diphenylindenyl anion (5b) produces 1,2,3-triphenylindene (8).In liquid ammonia and tetrahydrofuran more complex reaction pathways are observed.The regiochemistry of phenylation is attributed to radical attack at the most basic site, in accord with a previously published model.
- Tolbert, Laren M.,Siddiqui, Shahabuddin
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p. 1744 - 1751
(2007/10/02)
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- CUMULENE PHOTOCHEMISTRY: PHENYL AND HYDROGEN MIGRATION IN PHENYLALLENE PHOTOREACTIONS
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Photoreactions of tetra- and triphenylallene and 1,3,3-triphenylcyclopropane in hydrocarbon solvents are reported.Intermediacy of vinylcarbenes is supported by independent generation experiments.
- Klett, Michael W.,Johnson, Richard P.
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p. 2523 - 2526
(2007/10/02)
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- Sigmatropic Indenyl Rearrangements Induced by Electronic Excitation
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The photochemical rearrangement of several arylalkyl substituted indenes has been studied.The rearrangements were shown to be derived from the ?,?* singlet state since triplet sensitization led to no reaction or else resulted in a Paterno-Buchi
- Padwa, Albert,Goldstein, Steven,Loza, Roman,Pulwer, Mitchell
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p. 1858 - 1868
(2007/10/02)
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- Acidities of Indene and Phenyl-, Diphenyl-, and Triphenylindenes
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Equilibrium acidities in Me2SO for indene and 2-phenyl-, 3-phenyl-, 1,3-diphenyl-, 2,3-diphenyl-, and 1,2,3-triphenylindenes are reported.The pKa values for indene and 1,3-diphenylindene agree reasonably well with literature values once the lat
- Bordwell, F.G.,Drucker, George E.
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p. 3325 - 3328
(2007/10/02)
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