Pauson–Khand Adducts of <i>N</i>-Boc-propargylamine: A New Approach to 4,5-Disubstituted Cyclopentenones

Aiguabella, Nuria; Pesquer, Albert; Riéra, Antoni

doi:10.1021/ol400999a

Cited by 15 publications

(8 citation statements)

References 34 publications

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“…In the case of the intramolecular version, some of us previously demonstrated that fulleropyrrolidines endowed with one or two propargyl groups at the C-2 position of the pyrrolidine ring (1,6enynes) undergo the PKR leading to cyclopentenones fused to the fullerene moiety. 39,40 On the other hand, there are studies in which cyclopentenones are successfully synthesized via intermolecular PKR; [41][42][43][44] although this approach is more limited since olefins without strain are poorly reactive with the exception of ethylene. 45,46 Studies on the chemical functionalization of carbon nanostructures via the PKR are rather scarce and, to our knowledge, this cycloaddition has not been studied in single-walled carbon nanotubes (SWCNTs) yet.…”

Section: Introductionmentioning

confidence: 99%

Regioselectivity of the Pauson–Khand reaction in single-walled carbon nanotubes

et al. 2018

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Chemical functionalization of nanotubes, in which their properties can be combined with those of other classes of materials, is fundamental to improve the physicochemical properties of nanotubes for potential technological applications. In this work, we theoretically and experimentally examine the Pauson-Khand reaction (PKR) on zig-zag, armchair, and chiral single-walled carbon nanotubes (SWCNTs). Our benchmarked density functional theory (DFT) calculations show that an alternative pathway to the widely accepted Magnus reaction pathway has significantly lower energy barriers, thus suggesting the use of this alternative pathway to predict whether a PKR on SWCNTs is favored or hampered. Accessible energy barriers of up to 16 kcal mol-1 are estimated and our results suggest that semiconducting SWCNTs react faster than metallic ones, although both types can be functionalized. Guided by our theoretical predictions, cyclopentenones are successfully attached to SWCNTs by heating and are, subsequently, characterized in the laboratory.

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Section: Introductionmentioning

confidence: 99%

Regioselectivity of the Pauson–Khand reaction in single-walled carbon nanotubes

et al. 2018

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“…The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00810. Experimental details and 1 H and 13 C NMR, HRMS, and elemental analyses of new compounds (PDF)…”

Section: ■ Associated Contentmentioning

confidence: 99%

“…Other functional groups were well tolerated, and cyclopentenones containing coordinative alcohol and nitrile functional groups, 3h , i , were isolated in good yields. Norbornadiene was also an effective partner in the PKR, and adducts 3j – l were isolated in generally good yield.…”

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confidence: 98%

Nitrous Oxide Promoted Pauson–Khand Cycloadditions

et al. 2018

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A Pauson-Khand cycladdition of alkynes, alkenes, and carbon monoxide, promoted by cobalt carbonyl and nitrous oxide to furnish cyclopentenones is described. Preliminary mechanistic experiments suggest that nitrous oxide functions in a similar manner to the N-oxide promoters typically employed in Pauson-Khand reactions. Only dinitrogen and carbon dioxide are produced as a consequence of the activation mechanism, thus avoiding high molecular weight reagents and the build up of basic byproducts. The chemistry is done using equimolar amounts of alkyne, alkene, and dicobalt octacarbonyl, and is performed directly from the acetylenic component without having to presynthesize a cobalt-alkyne complex. Terminal acetylenes were suitable substrates, as was solid calcium carbide, and the corresponding adducts were isolated in good yields. Furthermore, two sequential [4+3] and [2+2+1] cycloadditions were performed, generating funtionalized cyclopentenones in only two steps from readily available starting materials.

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“…To circumvent the low reactivity and regioselectivity of linear internal olefins, Verdaguer and Riera devised an alternate route to 4,5-disubstituted cyclopentenones. [13] Their approached began with the PKR between a propargylamine-cobalt complex and norbornadiene. After a sequence of conjugate addition-elimination-conjugate addition-retro Diels-Alder, a 4,5-disubstituted cyclopentenone is produced (Scheme 6).…”

Section: Achiral/racemic Processesmentioning

confidence: 99%