Catalytic cyclization and competitive deactivation with Ru(PR2NR′2) complexes

Stubbs, J. M.; Bow, J. P. J.; Hazlehurst, R. J.; Blacquiere, Johanna M.

doi:10.1039/c6dt03694e

Cited by 11 publications

(21 citation statements)

References 22 publications

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“…(a) General scheme for the selective intramolecular hydroamination or hydroalkoxylation of alkynes via a Ru vinylidene intermediate. (b) Cooperative catalysts for alkyne hydrofunctionalization based on ruthenium, A and B , − and iron, 1a , b (reported in this work).…”

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“…Ruthenium complexes of the type Ru(Cp/Cp*)X(PR 3 ) 2 (Cp = cyclopentadienyl; Cp* = pentamethylcyclopentadienyl) are active catalysts for intramolecular hydroalkoxylation or hydroamination of alkynes to give O - and N -heterocycles, respectively. − Proton transfer steps within the catalytic cycle are promoted by a Brønsted base additive or by a basic site on the phosphine ligands, such as the pyridyl or tertiary amine groups in A and B , − respectively (Figure b). These metal–ligand cooperative catalysts − operate with faster rates and lower catalysts loadings in comparison to noncooperative analogues .…”

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endo-Selective Iron Catalysts for Intramolecular Alkyne Hydrofunctionalization

2020

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Metal–ligand cooperative iron complexes of the type [Fe(Cp*)(PR 2NPh 2)(MeCN)]PF6 (R = Cy, Ph) were synthesized and characterized. Both derivatives were active toward the intramolecular hydroamination of 2-ethynylaniline and hydroalkoxylation of 2-ethynylbenzyl alcohol. In the latter case, only the six-membered endo heterocycle isochromene was observed, which suggests that the alkyne is activated by a vinylidene mechanism. The reaction of [Fe(Cp*)(PCy 2NPh 2)(MeCN)]PF6 with phenylacetylene indeed afforded a complex that was characterized as a vinylidene, which implicates an analogous intermediate in the hydrofunctionalization mechanism.

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endo-Selective Iron Catalysts for Intramolecular Alkyne Hydrofunctionalization

2020

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“…Recently, Blacquiere and co‐workers reported the use of Ru catalysts supported by Cp and macrocyclic amine/phosphine‐mixed ligands (1,5‐ R ’‐3,7‐ R ‐1,5‐diaza‐3,7‐diphosphacyclooctane, P 2 N 2 ) to cyclize amine‐ and alcohol‐tethered alkynes for functionalized isochromenes, indoles and isoquinolinones (Scheme ) . The amine groups on the P 2 N 2 were proposed to serve as proton shuttles in the catalytic cycle.…”

Section: Recent Progress Of Ruthenium‐induced Cyclization Of Alkynesmentioning

confidence: 99%

“… Ru‐catalyzed cycloisomerizations of hydroxyl‐ and amine‐substituted alkynes into isochromenes, indoles and isoquinolinones developed by Blacquiere and co‐workers …”

Section: Recent Progress Of Ruthenium‐induced Cyclization Of Alkynesmentioning

confidence: 99%

“…[14] Recently,B lacquiere and co-workers reported the use of Ru catalysts supported by Cp andm acrocyclic amine/phosphinemixed ligands (1,5-R'-3,7-R-1,5-diaza-3,7-diphosphacyclooctane, P 2 N 2 )t oc yclize amine-and alcohol-tethereda lkynes for functionalized isochromenes, indoles and isoquinolinones (Scheme 9). [15][16][17] The amine groups on the P 2 N 2 were proposed to serve as protons huttles in the catalytic cycle. The presence of Ru-vinylidene intermediacy was supported by the detection of deactivation products originated from the nucleophilic attacks of amine pendantstoR u-vinylidene intermediates.…”

Section: Catalytic Ru II -Mediated Cyclizations Of N/o-functionalizedmentioning

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Ruthenium‐Induced Cyclization of Heteroatom‐Functionalized Alkynes: Progress, Challenges and Perspectives

Chung

Yeung

Wong

2020

Chemistry A European J

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Metal-induced cyclization of functionalized alkynes represents one of the most general approaches to prepare organic heterocycles. AlthoughR u II centers are well-established to promote alkyne to vinylidener earrangements and many Ru II -mediated alkyne cyclizations have been rationalized to be the resultso fp ost-vinylidene transformations, recent discoveries indicate that Ru II centers can serve as electrophiles and induce alkyne cyclizationsw ithoutv inylidene intermediacy. In this Minireview,a no verview of the Ru II -induced cyclization of heteroatom-functionalized alkynes in the last decadei sp rovided, with an emphasis on the discoveries and validations of the unconventional "non-vinylidene-involving" pathways. Recent Progress of Ruthenium-Induced Cyclization of AlkynesResearcho nt he activation of heteroatom-functionalizeda lkynes by Ru II complexes for oxygen-and nitrogen-containing heterocycles of different ring sizes (5-to 8-membered) continues unabated. Most reported Ru complexes ares upported by Cp (Cp = cyclopentadienyl) or structurally analogous h 5 -ligands, amine-or mixed amine/phosphine-basedc helates. In general, the catalyst loadings are almost lower than 10 mol %a nd can be as low as 0.5 mol %. Although the cyclizations are mostly demonstrated with terminala lkynes, there are increasing number of successful reports on cyclizing internal alkynes.T he use of proton shuttles( internal or external bases which facilitate protont ransfer) has been found to be critical in many of these catalytic reactions. Noteworthy,s everal recent studies clearly indicatet hat the "vinylidene-involving" and "non-vinylidene-involving" pathwaysd epicted in Scheme 1are competing mechanisms. In this section, Ru-catalyzedc yclization of heteroatom-functionalized alkynes in the last decade is discussed in chronological order,e xcept in the cases of certain serial or outlying works. Catalytic Ru II -mediated cyclizations of N/O-functionalized alkynesthrough "vinylidene-involving" pathwaysThe successful isolations of Fe-, Ru-, and Os-oxacarbene complexesf rom the reactions between homopropargylic/bis-ho-Scheme1.(a) Established mechanisms for the formation of Ru-vinylidene species. (b) Electrophilic cyclizationso fheteroatom-functionalized alkynes induced by Ru.[a] Dr.Scheme8.Ru-catalyzed cycloisomerizations of alkynols into 5-, 6-and 7membered oxacycles developed by Jia and co-workers. [13,14] Scheme7.Ru-catalyzed cyclizationso fa niline-and phenol-tethered alkynes into indoles and benzofurans, respectively developed by Grotjahn and coworkers. [11,12] Scheme9.Ru-catalyzed cycloisomerizations of hydroxyl-and amine-substituteda lkynes into isochromenes, indolesa nd isoquinolinones developedby Blacquiereand co-workers. [15][16][17] Scheme10. Ru-catalyzed cycloisomerizations of alcohol-tethered alkynes developedb yWen and co-workers. [18] Chem.E ur.Scheme20. Isolation of, and proposed formation mechanism for 4a.The synthesis of 4b is also depictedf or reference [31].Scheme21. Isolation of, and proposed formation mechanism for...

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Catalyst Pendent‐Base Effects on Cyclization of Alkynyl Amines

et al. 2018

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A family of [CpRu(PP)(MeCN)]PF6 complexes (2 a–e and 4) were prepared in which the bis‐phosphine ligand contains a pendent tertiary amine in the second‐coordination sphere. 2 a–e contain PPh2NR′2 ligands with two amine groups as the pendent base. Complex 4 has the PPh2NPh1 ligand with only one pendent amine. The catalytic performance of 2 a–e and 4 were assessed in the cyclization of 2‐ethynyl aniline and 2‐ethynylbenzyl alcohol. It was revealed that the positioning of the pendent amine near the metal active site is essential for high catalyst performance. A comparison of PPh2NR′2 catalysts (2 a–e) showed minimal difference in performance as a function of pendent amine basicity. Rather, only a threshold basicity – in which the pendent amine was more basic than the substrate – was required for high performance.

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Catalytic cyclization and competitive deactivation with Ru(P^R₂N^R′₂) complexes

Cited by 11 publications

References 22 publications

endo-Selective Iron Catalysts for Intramolecular Alkyne Hydrofunctionalization

endo-Selective Iron Catalysts for Intramolecular Alkyne Hydrofunctionalization

Ruthenium‐Induced Cyclization of Heteroatom‐Functionalized Alkynes: Progress, Challenges and Perspectives

Catalyst Pendent‐Base Effects on Cyclization of Alkynyl Amines

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