- Substituted 9-Anthraldehydes from Dibenzocycloheptanol Epoxides via Acid-Catalyzed Epoxide Opening/Semipinacol Rearrangement
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Starting from benzaldehyde derivatives, the corresponding dibenzocycloheptenol could be prepared in five steps. Under both substrate (secondary vs tertiary alcohol and the substituents on the aromatic ring(s)) and condition control, the subsequent epoxidation and acid-catalyzed epoxide opening/semipinacol rearrangement/aromatization afforded the corresponding 9-anthraldehydes in good yields, up to 88% over two steps. The presence of the electron-withdrawing group(s) on the aromatic ring(s) suppressed the rate of the epoxidation while the subsequent semipinacol rearrangement step required heating; the presence of the electron-donating group(s), on the other hand, frequently led to the decomposition during the epoxidation. From the mechanistic studies, the semipinacol rearrangement of the epoxide could precede the ionization at the bisbenzylic position, yielding the aldehyde intermediate. The ensuing dehydrative aromatization led to the formation of 9-anthraldehyde. Conversely, nucleophilic addition to the aldehyde and dehydrative aromatization with concomitant loss of formic acid led to anthracene.
- Phumjan, Tanawat,Songthammawat, Poramate,Jongcharoenkamol, Jira,Batsomboon, Paratchata,Ruchirawat, Somsak,Ploypradith, Poonsakdi
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p. 13322 - 13349
(2021/09/13)
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- Unraveling relation between nonlinear absorption and structure of push pull ornamented anthracenyl chalcone derivatives
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Using green chemical method a series of fifteen systematically substituted 3-(9-substituted anthracen-10-yl)-1-(4-phenyl substituted)prop-2-en-1-one derivatives having high nonlinear absorption coefficient have been synthesized. The nonlinear absorption properties of these compounds were studied using nanosecond pulses at 532 nm wavelength. All 15 derivatives are found to show high nonlinear absorption in the range of 35–640 cm/GW. Among these the derivatives with –NO2 as one of the substitution group show higher nonlinear absorption. The origin of high nonlinear absorption with low linear absorption in the compounds has been attributed to two-step two-photon absorption process. We have shown that the energy bands of these compounds are distributed such that for excitation at 532 nm they have strong nonlinear absorption. These properties of the reported compounds make them a potential candidate for biological imaging and other applications which are based on nonlinear absorption.
- Chari, Rama,Jayabalan, J.,Saha, Amrita,Singh, Asha
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- Orthoamides. LIII. A New Synthesis for Aromatic Aldehydes of Wide Scope
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Diformamide (1) reacts with activated aromatic compounds like toluene, anisole, m-xylene, 1,2-dimethoxybenzene in the presence of AlCl3 to give N-(diarylmethyl)-formamides 2a-d, the corresponding aromatic aldehydes 3-6 are formed as by-products in low yields. From N,N-dimethylaniline and 1/AlCl3 the triphenylmethane derivative 7 can be obtained. The reaction of anisole with N-methyl-diformamide (9) affords the formamide 10. The mixture of formamide, P4O10 and AlCl3 reveals to be a reagent which is capable to formylate toluene and anisole, resp. Triformamide (14)/AlCl3 is an effective formylating system which allows the preparation of aromatic aldehydes (e.g. 3,4,17-32) from the corresponding aromatic hydrocarbons. Aluminiumchloride can be replaced by borontrichloride. The yields of the formylation reactions depend strongly from the reaction conditions (molar ratio: aromatic hydrocarbon/ AlCl3/14; solvent, reaction temperature). The scope of the reaction covers nearly complete those of the Gattermann-Koch-, Gattermann- and Vilsmeier-Haack-reaction.
- Kantlehner, Willi,Vettel, Markus,Gissel, Alexander,Haug, Erwin,Ziegler, Georg,Ciesielski, Michael,Scherr, Oliver,Haas, Richard
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p. 297 - 310
(2007/10/03)
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- Process for nucleophilic fluoroalkylation of aldehydes
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Aryl difluoromethyl sulfone adds to alkehydes under phase transfer conditions to give novel substituted alcohols of the general formula wherein R is an aryl, cycloaliphatic, sec- or tert-aliphatic, or heterocyclic group and Ar is an aryl group. The substituted alcohols of formula I are of particular utility as intermediates in the synthesis of a variety of useful end products. For example, the products of formula I may be utilized in desulfonylation reactions, oxidation reactions and fluorination reactions.
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- IODOXYBENZENE A REMARKABLY CLOSE OZONE EQUIVALENT
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Iodoxybenzene is isoelectronic to ozone and several of its reactions proceed via pathways remarkably similar to that of ozone.An attractive feature of iodoxybenzene mediated reactions is the direct formation of products and the transformation of the reagent to iodobenzene.The formation of benzil and iodobenzene in good yields from diphenylacetylene provides support for the anticipated intermediate arising from ?4s+?2s addition.Iodoxybenzene transforms phenanthrene to phenanthrenequinone as a result of the initially formed 4+2 adduct undergoing C-H rupture, in preference to the C-C rupture.This change is parallel to the transformation of phenanthrene 9-carboxylic acid to phenanthrenequinone with ozone.The expected C-C rupture of the initially formed adduct does take place with acenaphthylene leading to naphthalic anhydride.The reaction of pyrene with iodoxybenzene leads to nearly equal amounts of the 4-5, 1-6 and 3-6 quinones involving attack on the bond of the lowest bond localisation energy and the atom of the lowest atom localization energy.This behaviour is similar to the action of ozone on benzopyrene.Iodoxybenzene transforms anthracene, just like ozone, to anthraquinone, in good yields.The involvement of transannular addition of iodoxybenzene, as is partly the case with ozone, is proved unlikely by reaction with 9, 10 dimethylanthracene which gave 10-methyl 9-anthraldehyde and 10-carboxy 9-anthraldehyde, involving the insertion of elements of iodoxybenzene to the aryl C-H bond.This tendency of iodoxybenzene has been further demonstrated by the following changes: diphenylmethane-->benzophenone; fluorene-->fluorenone and tetralin-->α-tetralone.Several of the transformations brought about with iodoxybenzene provide attractive synthetic routes, particularly to phenanthrenequinone, pyrenequinones and tetralone.Finally, just like the 2O3 --> 3O2 change, iodoxybenzene, and even more so, 4-iodoxybiphenyl, thermally fragment to iodobenzene and 4-iodobiphenyl.
- Ranganathan, S.,Ranganathan, D.,Ramachandran, P. V.
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p. 3145 - 3152
(2007/10/02)
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- Oxidation of Benzylic Hydrocarbons with Benzeneseleninic Anhydride and Related Reactions
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The use of benzeneseleninic anhydride as a new side-chain oxidant for a variety of aromatic and heteroaromatic hydrocarbons has been investigated.The oxidation normally proceeds well for simple substrates, neat or in chlorobenzene solution at 100-130 deg C.In examples where the aromatic rings are susceptible towards electrophilic attack selenated compounds are usually formed as the major by-products.
- Barton, Derek H. R.,Hui, Raymond A. H. F.,Ley, Steven V.
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p. 2179 - 2186
(2007/10/02)
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