Dataset Information

Auto-Tandem Catalysis: Pd^II -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

ABSTRACT: A Pd^II catalyst system has been used to successfully catalyse two mechanistically distinct reactions in a one-pot procedure: dehydrogenation of 2,2-disubstituted cyclopentane-1,3-diones and the subsequent oxidative Heck coupling. This auto-tandem catalytic reaction is applicable to both batch and continuous flow processes, with the latter being the first example of a tandem aerobic dehydrogenation/oxidative Heck in flow. In addition, a telescoped reaction involving enantioselective desymmetrisation of the all-C quaternary centre was successfully achieved.

SUBMITTER: Lamb CJC

PROVIDER: S-EPMC5767738 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Publications

Auto-Tandem Catalysis: Pd<sup>II</sup> -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

Lamb Claire J C CJC Nderitu Bryan G BG McMurdo Gemma G Tobin John M JM Vilela Filipe F Lee Ai-Lan AL

Chemistry (Weinheim an der Bergstrasse, Germany) 20171130 72

A Pd<sup>II</sup> catalyst system has been used to successfully catalyse two mechanistically distinct reactions in a one-pot procedure: dehydrogenation of 2,2-disubstituted cyclopentane-1,3-diones and the subsequent oxidative Heck coupling. This auto-tandem catalytic reaction is applicable to both batch and continuous flow processes, with the latter being the first example of a tandem aerobic dehydrogenation/oxidative Heck in flow. In addition, a telescoped reaction involving enantioselective de ...[more]

PMID: 29105890

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Project description:In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl2 complexes {Cl2Co[P~P]} and Me3Al or methylaluminoxane, acyclic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydrovinylation products. The regioselectivity (1,4- or 1,2-addition) and the alkene configuration (E- or Z-) of the resulting product depend on the nature of the ligand and temperature at which the reaction is carried out. Cobalt(II)-complexes of 1,1-diphenylphosphinomethane and similar ligands with narrow bite angles give mostly 1,2-addition, retaining the E-geometry of the original diene. Complexes of most other ligands at low temperature (-40 °C) give almost exclusively a single branched product, (Z)-3-alkylhexa-1,4-diene, which arises from a 1,4-hydrovinylation reaction. A minor product is the linear adduct, a 5-alkyl-hexa-1,4-diene, also arising from a 1,4-addition of ethylene. As the temperature is increased, a higher proportion of the major 1,4-adduct appears as the (E)-isomer. The unexpectedly high selectivity seen in the Co-catalysed reaction as compared to the corresponding Ni-catalysed reaction can be rationalized by invoking the intermediacy of an η4-[(diene)[P~P]CoH]+-complex and its subsequent reactions. The enhanced reactivity of terminal E-1,3-dienes over the corresponding Z-dienes can also be explained on the basis of the ease of formation of this η4-complex in the former case. The lack of reactivity of the X2Co(dppb) (X = Cl, Br) complexes in the presence of Zn/ZnI2 makes the Me3Al-mediated reaction different from the previously reported hydroalkenylation of dienes. Electron-rich phospholanes, bis-oxazolines and N-heterocyclic carbenes appear to be poor ligands for the Co(II)-catalysed hydrovinylation of 1,3-dienes. An extensive survey of chiral ligands reveals that complexes of DIOP, BDDP and Josiphos ligands are quite effective for these reactions even at -45 °C and enantioselectivities in the range of 90-99 % ee can be realized for a variety of 1,3-dienes. Cobalt(II)-complex of an electron-deficient Josiphos ligand is especially active, requiring only <1 mol% catalyst to effect the reactions.

Dataset Information

Auto-Tandem Catalysis: Pd^II -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

Publications

Auto-Tandem Catalysis: Pd<sup>II</sup> -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

Similar Datasets

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Dataset Information

Auto-Tandem Catalysis: PdII -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

Publications

Auto-Tandem Catalysis: Pd<sup>II</sup> -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Auto-Tandem Catalysis: Pd^II -Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane-1,3-diones.