- A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives
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Fe(BF4)2·6H2O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)2 can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.
- Chowdhury, Abhishek Dutta,Lahiri, Goutam Kumar
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supporting information; experimental part
p. 3448 - 3450
(2012/05/20)
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- Product studies and laser flash photolysis on alkyl radicals containing two different β-leaving groups are consonant with the formation of an olefin cation radical
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1-Bromo-2-methoxy-1-phenylpropan-2-yl (3) and 2-methoxy-1-phenyl-1-diphenylphosphatopropan-2-yl (4) were generated under continual photolysis from the respective PTOC precursors in a mixture of acetonitrile and methanol. The radicals undergo heterolytic fragmentation of the substituent in the β-position to generate the olefin cation radical (5). Z-2-Methoxy-1-phenylpropene (15) is the major product formed in the presence of 1,4-cyclohexadiene, and is believed to result from hydrogen atom transfer to the oxygen of the olefin cation radical, followed by deprotonation. Laser flash photolysis experiments indicate that reaction between 5 and 1,4-cyclohexadiene occurs with a rate constant of ~6 × 105 M-1 s-1. 2,2-Dimethoxy-1-phenylpropane (18) is observed as a minor product. Laser flash photolysis experiments place an upper limit on methanol trapping of 5 at k 3 M-1 s-1 and do not provide any evidence for the formation of reactive intermediates other than 5. The use of two PTOC precursors containing different leaving groups to generate a common olefin cation radical enables one to utilize product analysis to probe for the intermediacy of other reactive intermediates. The ratio of 15:18 is dependent upon hydrogen atom donor concentration, but is independent of the PTOC precursor. These observations are consistent with the proposal that both products result from trapping of 5 that is formed via heterolysis of 3 and 4.
- Bales,Horner,Huang,Newcomb,Crich,Greenberg
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p. 3623 - 3629
(2007/10/03)
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- Synthesis and structures of heterobimetallic Ir2M (M=Pd, Pt) sulfido clusters and their catalytic activity for regioselective addition of alcohols to internal 1-aryl-1-alkynes
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The heterobimetallic trinuclear suffido clusters [(Cp*Ir)2(μ3-S)2MCl2] (M = Pd (3), Pt (4); Cp* = η5-C5Me5) were synthesized from the dinuclear hydrogensulfido complex [Cp*IrCl(μ
- Masui, Dai,Kochi, Takuya,Tang, Zhen,Ishii, Youichi,Mizobe, Yasushi,Hidai, Masanobu
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- Regioselective addition of alcohols to internal 1-aryl-1-alkynes catalyzed by a triangular heterobimetallic Ir2Pd sulfido cluster
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The triangular heterobimetallic sulfido cluster [(Cp*Ir)2(μ3-S)2PdCl2] prepared from [PdCl2(cod)] and [Cp*IrCl(μ-SH)2IrCp*Cl] was found to catalyze the addition of alcohols to alkynes to give the corresponding ketals. In particular, internal 1-aryl-1-alkynes were transformed into the corresponding 2,2-dialkoxy-1-arylalkanes with high regioselectivity. The analogous Ir2PtS2 cluster proved to be much less selective.
- Masui, Dai,Ishii, Youichi,Hidai, Masanobu
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p. 717 - 718
(2007/10/03)
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- Intramolecular meta photocycloaddition of conformationally restrained 5-phenylpent-1-enes. Part II: Steric and electronic effects caused by 4-mono- and 4-disubstitution
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The meta photocycloaddition of 4-substituted 5-phenylpent-1-enes. 10-18, has been studied. The monosubstituted derivatives always prefer 2,6 addition, independent of the size of the substituent. For 2,6 addition two basic conformations are possible. Disubstituted compounds yield predominantly 1,3 addition with the sterically more demanding group exo. Except for the methoxymethyl and THF derivative the oxygen is found exo as a result of repulsion, while the monohydroxy derivative gives also endo which might be explained by hydrogen bonding. The products from compound 11 change from mainly endo-OH in cyclohexane to chiefly exo-OH in methanol. Much similarity is found with Diels-Alder cycloaddition.
- Barentsen, Helma M.,Sieval, Alex B.,Cornelisse, Jan
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p. 7495 - 7520
(2007/10/02)
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- Reactions of O,O-Diprotonated Nitro Olefins with Benzenes. Formations of Phenylacetones, 4H-1,2-Benzoxazines and Biarylacetone Oximes
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O,O-Diprotonated nitro olefins undergo three alternative electrophilic reactions which yield α-phenylacetones, 4H-1,2-benzoxazines and biphenylacetone oximes depending on the reaction conditions (temperature and time) and aromatic substrates.Although these reactions are seemingly divergent, a common intermediate of a phenylated protonated aci-nitro species, derived from the dication, is postulated to be involved in the reactions.Furthermore, the formation of benzoxazines and biphenylacetone oximes can be interpreted in terms of participation of novel chemical species with phenylethylene dication character derived from the common intermediate.
- Ohwada, Tomohiko,Okabe, Kazuaki,Ohta, Toshiharu,Shudo, Koichi
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p. 7539 - 7555
(2007/10/02)
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- Novel Electrophilic Species Equivalent to α-Keto Cations. Reactions of O,O-Diprotonated Nitro Olefins with Benzenes Yield Arylmethyl Ketones
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The N,N-dihydroxyiminium carbenium ions formed by O,O-diprotonation of nitro olefins in a strong acid, trifluoromethanesulfonic acid (TFSA), are discrete and novel dipositively charged species.The dications formed from α-substitited nitroethylenes are reactive electrophiles to give α-arylated ketones in high yields.This constitutes a versatile synthetic method for the preparation of α-arylated ketones, which are difficult to synthesize by the conventional Friedel-Crafts reactions.
- Okabe, Kazuaki,Ohwada, Tomohiko,Ohta, Toshiharu,Shudo, Koichi
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p. 733 - 734
(2007/10/02)
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- ELECTROOXIDATIVE REARRANGEMENT OF CONJUGATED ARYLOLEFINS TO ARYLACETALDEHYDE DIMETHYL ACETALS
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Electrochemical oxidation of conjugated arylolefins 1 in trimethyl orthoformate containing iodine gave arylacetaldehyde dimethyl acetals 2 in high yields.
- Shono, Tatsuya,Matsumura, Yoshihiro,Katoh, Susumu,Ikeda, Kaoru,Fujita, Tetsuhiro,Kamada, Tohru
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p. 5309 - 5312
(2007/10/02)
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- Process for producing phenylacetones
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A phenylacetone or its derivative having the general formula (I): STR1 wherein X, Y, and Z are independently a hydrogen atom, a hydroxyl group, a halogen atom, a nitro group, an amino group, a lower alkyl group having 1 to 6 carbon atoms, a lower alkoxy group having 1 to 6 carbon atoms, or a benzyloxy group and any two substituents of X, Y, and Z may form, together with the benzene ring, a heterocycling ring having 5 to 7 members including 1 or 2 oxygen atoms is produced at a high yield and a high selectivity by reacting a 3-phenylpropylene or its derivative having the general formula (II): STR2 wherein X, Y, and Z are as defined above, with an alkyl nitrite having the general formula (III): wherein R is an aliphatic, aromatic, or alicyclic saturated or unsaturated hydrocarbon group in the presence of (a) water, (b) an alcohol, (c) a palladium catalyst, and (d) an optional amine or copper compound, or by reacting the above-mentioned 3-phenylpropylene or its derivative with the above-mentioned alkyl nitrite in the presence of (a) an alcohol, (b) a palladium catalyst and (c) an optional amine or copper compound to form 1-phenyl-2,2-dialkoxypropane or it derivative having the general formula (IV): STR3 wherein X, Y, Z and R are as defined above, followed by hydrolyzing the reaction product.
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- CONVERSION OF ALKYL PHENYL SELENIDES AND SELENOXIDES INTO DIALKYL ETHERS. NUCLEOFUGACITY ENHANCEMENT OF THE PLENYLSELENINYL GROUP BY meta-CHLOROPERBENZOIC ACID IN ALCOHOLS
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The recently reported conversion of alkyl phenyl selenides into dialkyl ethers, promoted by MCPBA in alcohols, has been reinvestigated.It is concluded that the reactive intermediate does not derive from the selenones, as reported, but from the selenoxides.It is suggested that MCPBA adds to the selenoxide function to give an intermediate which easily gives rise to solvolysis; thus, the addition of MCPBA greatly enhances the nucleofugacity of the phenylseleninyl group.The synthesis and the reactivity of several 1-phenyl, 2-phenylseleninyl- and 1-phenyl-, 2-phenylselenonyl-ethanes are also described.
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Chianelli, Donatella,Bartoli, Donatella
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p. 423 - 428
(2007/10/02)
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- Halogenative Deoxygenation of Ketones; Vinyl Bromides and/or gem-Dibromides by Cleavage of 1,3-Benzodioxoles (Ketone Phenylene Acetals) with Boron Tribromide
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Representative ketones 1 have been converted in generally good yields to the respective 1,3-benzodioxoles 5 by trans-acetalization of ketone dimethyl acetals with 1,2-dihydroxybenzene, and cleaved with boron tribromide. 1,3-Benzodioxoles derived from α-unbranched aliphatic ketones gave in general a mixture of vinyl bromides and gem-dibromides; pure gem-dibromides could be selectively obtained in most of cases using a suitable reaction time. 1,3-Benzodioxoles derived from α-branched ketones gave complex mixtures and their cleavage appears to be of little synthetic signifance. 1,3-Benzodioxoles of aromatic ketones gave vinyl bromides only.Aliphatic cyclic gem-dibromides 3 were converted to the respective vinyl bromides 2 by phase-transfer-catalysed dehydrobromination.
- Napolitano, Elio,Fiaschi, Rita,Mastrorilli, Ettore
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p. 122 - 125
(2007/10/02)
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- SOLVOHYPERIODINATION. A COMPARISON WITH SOLVOTHALLATION
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C6H5IO/CH3OH and a catalyst such as FSO3H, CF3SO3H or BF3-Et2O as well as C6H5(OH)OTs-CH3OH, react with chalcones, acetophenones and styrenes to yield rearranged products.The overall course of these reactions is analogous to that of Tl(NO3)3-CH3OH in reaction with the same compounds.
- Moriarty, Robert M.,Khosrowshahi, Jaffar S.,Prakash, Om
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p. 2961 - 2964
(2007/10/02)
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