- Heck Reactions of Acrolein or Enones and Aryl Bromides – Synthesis of 3-Aryl Propenals or Propenones and Consecutive Application in Multicomponent Pyrazole Syntheses
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3-(Hetero)aryl propenals or propenones are efficiently prepared by a Heck reaction of (hetero)aryl bromides and acrolein or vinyl ketones using Beller's CataCXium Ptb ligand under Jeffery's and Fu's conditions. The formation of these three-carbon building blocks is embedded into consecutive three- and pseudo-four-component syntheses of 3-(hetero)aryl and 3,5-diarylpyrazoles with a broad substitution pattern in moderate to excellent yield.
- Stephan, Marvin,Panther, Jesco,Wilbert, Fabio,Ozog, Pauline,Müller, Thomas J. J.
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supporting information
p. 2086 - 2092
(2020/03/23)
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- Phosphorous acid promoted isomerization of propargyl alcohols to α,β-unsaturated carbonyl compounds
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A metal-free and two-phase protocol for the Meyer-Schuster isomerization of propargyl alcohols to the corresponding α,β-unsaturated carbonyl compounds has been achieved in the presence of stoichiometric phosphorous acid aqueous solution, which produces the desired products in high yields with excellent stereoselectivity. Compared with the traditional methods, the procedure features broad scope of the substrates, mild conditions, and easy separation, providing an appealing alternative to the Meyer-Schuster reaction.
- Gan, Xiaotang,Fu, Zuqi,Liu,Yan, Yani,Chen, Chao,Zhou, Yongbo,Dong, Jianyu
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- Expanding the scope of the Babler–Dauben oxidation: 1,3-oxidative transposition of secondary allylic alcohols
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We report the catalytic chromium-mediated oxidation of secondary allylic alcohols to give α,β-unsaturated aldehydes with exclusive (E)-stereoselectivity. This facile procedure employs catalytic PCC (5?mol?%) and periodic acid (H5IO6) as a co-oxidant. This transformation occurs specifically with aromatic substituted allyl alcohols containing both electron withdrawing and electron donating substituents as well as a range of functional groups.
- Killoran, Patrick M.,Rossington, Steven B.,Wilkinson, James A.,Hadfield, John A.
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supporting information
p. 3954 - 3957
(2016/08/09)
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- Biphilic organophosphorus catalysis: Regioselective reductive transposition of allylic bromides via PIII/PV redox cycling
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We report that a regioselective reductive transposition of primary allylic bromides is catalyzed by a biphilic organophosphorus (phosphetane) catalyst. Spectroscopic evidence supports the formation of a pentacoordinate (σ5-P) hydridophosphorane as a key reactive intermediate. Kinetics experiments and computational modeling are consistent with a unimolecular decomposition of the σ5-P hydridophosphorane via a concerted cyclic transition structure that delivers the observed allylic transposition and completes a novel PIII/PV redox catalytic cycle. These results broaden the growing repertoire of reactions catalyzed within the PIII/PV redox couple and suggest additional opportunities for organophosphorus catalysis in a biphilic mode.
- Reichl, Kyle D.,Dunn, Nicole L.,Fastuca, Nicholas J.,Radosevich, Alexander T.
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p. 5292 - 5295
(2015/05/13)
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- Diastereoselective Fluorocyclopropanation of Chiral Allylic Alcohols Using an α-Fluoroiodomethylzinc Carbenoid
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Chiral fluorocyclopropyl carbinols were synthesized in high diastereoselectivities via a zinc mediated cyclopropanation reaction, using sec-allylic alcohols as simple building blocks. An enantioselective version of this transformation was achieved through
- Navuluri, Chandrasekhar,Charette, André B.
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supporting information
p. 4288 - 4291
(2015/09/15)
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- Direct synthesis of 3-arylpropionic acids by tetraphosphine/palladium catalysed Heck reactions of aryl halides with acrolein ethylene acetal
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Through the use of [PdCl(C3H5)]2/Cis,cis, cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as a catalyst, a range of aryl bromides undergoes Heck reaction with acrolein ethylene acetal. With this acetal, the selective formation of 3-arylpropionic acids/esters was observed. The functional group tolerance on the aryl halide is remarkable; substituents such as fluoro, methyl, methoxy, acetyl, formyl, benzoyl, nitro or nitrile are tolerated. Furthermore, this catalyst can be used at low loading, even for reactions of sterically hindered aryl bromides. Graphical Abstract.
- Lemhadri, Mhamed,Doucet, Henri,Santelli, Maurice
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p. 11533 - 11540
(2007/10/03)
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