- Copper-catalyzed hydroformylation and hydroxymethylation of styrenes
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Hydroformylation catalyzed by transition metals is one of the most important homogeneously catalyzed reactions in industrial organic chemistry. Millions of tons of aldehydes and related chemicals are produced by this transformation annually. However, most of the applied procedures use rhodium catalysts. In the procedure described here, a copper-catalyzed hydroformylation of alkenes has been realized. Remarkably, by using a different copper precursor, the aldehydes obtained can be further hydrogenated to give the corresponding alcohols under the same conditions, formally named as hydroxymethylation of alkenes. Under pressure of syngas, various aldehydes and alcohols can be produced from alkenes with copper as the only catalyst, in excellent regioselectivity. Additionally, an all-carbon quaternary center containing ethers and formates can be synthesized as well with the addition of unactivated alkyl halides. A possible reaction pathway is proposed based on our results. This journal is
- Franke, Robert,Geng, Hui-Qing,Meyer, Tim,Wu, Xiao-Feng
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p. 14937 - 14943
(2021/12/02)
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- Synthesis of rac-ɑ-aryl propionaldehydes via branched-selective hydroformylation of terminal arylalkenes using water-soluble Rh-PNP catalyst
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This work detailed the preparation of a class of water-soluble PNP ligands that differed by the nature of the substitute on phenyl ring of ligands. These ligands were incorporated into water-soluble rhodium-PNP complex catalysts that were used to regioselective hydroformylation of a series of terminal arylalkenes, providing efficient access to rac-α-aryl propionaldehydes in good to excellent yield (up to 97%) and branched-regioselectivity (up to 40:1 b/l ratio). Furthermore, gram-scale and diverse synthetic transformation demonstrated synthetic application of this methodology for non-steroidal antiinflammatory drugs.
- Chen, Fen-Er,Gao, Peng,Ke, Miaolin,Liang, Guanfeng,Ru, Tong
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- Synthesis of tetra-pincer nickel(ii) and palladium(ii) complexes of resorcin[4]arene-octophosphinite [Res(OPR2)8] and rhodium-catalyzed regioselective hydroformylation reaction
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The condensation reaction of resorcinol with pentanal yielded resorcin[4]arene 1 which on bromination using N-bromosuccinimide at room temperature produced tetra-bromide derivative 2. The reactions of 2 with chlorodiphenylphosphine and o-phenylenephosphoro-chloridite yielded octaphosphinite 3 (hereafter referred to as octaphos) and octaphosphite 4, respectively. The reactions of 3 with Ni(COD)2 or Pd2(dba)3·CHCl3 in appropriate molar ratios yielded tetra-pincer complexes 5 and 6, respectively. The structures of both the complexes were established by single crystal X-ray diffraction studies. The resorcin[4]arene backbone adopts a boat structure in these complexes. Typically, the Rh-catalyzed hydroformylation of styrene prevalently delivers a branched (b) chiral aldehyde. A unique resorcin[4]arene skeleton based octaphos 3 was employed in the Rh-catalyzed hydroformylation of styrene. The hydroformylation of styrene with a metal to ligand ratio of 1:1 (M:L) was found to be regioselective, producing a linear (l) aldehyde as a major product with 100% conversion in 3 h. The l:b ratio surprisingly increased when the ortho positions of styrene were populated by methyl and chloro substituents. The hydroformylation of p-nitro styrene triggered a remarkably high linear:branched aldehyde ratio of 2.4 (71% linear aldehyde) despite its electron withdrawing nature. The highest linear selectivity of 97% (l:b ratio 27.8) was achieved in the case of 2,4,6-trimethylstyrene.
- Ananthnag, Guddekoppa S.,Mondal, Dipanjan,Mague, Joel T.,Balakrishna, Maravanji S.
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p. 14632 - 14641
(2019/10/16)
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- Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
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Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid-liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid-liquid separator both play an essential role in enabling these telescoped flow processes.
- Bourne, Samuel L.,O'Brien, Matthew,Kasinathan, Sivarajan,Koos, Peter,Tolstoy, Paeivi,Hu, Dennis X.,Bates, Roderick W.,Martin, Benjamin,Schenkel, Berthold,Ley, Steven V.
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p. 159 - 172
(2013/03/13)
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- Enantioselective organocatalytic formal allylation of α-branched aldehydes
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Heteroarylvinyl sulfone 1 has been successfully used as a new sulfonyl Michael acceptor in aminocatalytic reactions with branched aldehydes. Subsequent one-pot Julia-Kocienski olefination allows the challenging preparation of enantiomerically pure α-allylated aldehydes bearing C-α quaternary carbons.
- Rodrigo, Eduardo,Morales, Sara,Duce, Sara,Ruano, Jose Luis Garcia,Cid, M. Belen
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supporting information; scheme or table
p. 11267 - 11269
(2011/12/05)
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- Syngas-mediated C-C bond formation in flow: Selective rhodium-catalysed hydroformylation of styrenes
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We report a continuous flow, rhodium-catalysed hydroformylation of various styrenes using a tube-in-tube gas-liquid reactor. The flow process afforded selectively branched aryl aldehydes in good yields. Georg Thieme Verlag Stuttgart · New York.
- Kasinathan, Sivarajan,Bourne, Samuel L.,Tolstoy, P?ivi,Koos, Peter,Obrien, Matthew,Bates, Roderick W.,Baxendale, Ian R.,Ley, Steven V.
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scheme or table
p. 2648 - 2651
(2011/12/04)
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- Catalytic asymmetric reductive amination of aldehydes via dynamic kinetic resolution
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A novel organocatalytic asymmetric reductive amination of aldehydes has been developed. Treating racemic α-branched aldehydes with p-anisidine and a Hantzsch ester in the presence of our previously developed phosphoric acid catalyst, TRIP, gave β-branched secondary amines in excellent yields and enantioselectivities via an efficient dynamic kinetic resolution. The process is applicable to several different aromatic aldehydes and amines but gives slightly reduced enantiomeric ratios with aliphatic aldehydes. Copyright
- Hoffmann, Sebastian,Nicoletti, Marcello,List, Benjamin
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p. 13074 - 13075
(2008/02/08)
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