ChemInform Abstract: Cycloisomerization of Aromatic Homo‐ and Bis‐homopropargylic Alcohols via Catalytic Ru Vinylidenes: Formation of Benzofurans and Isochromenes.

Varela-Fernández, Alejandro; González-Rodrı́guez, Carlos; Varela, J.; Castedo, Luís; Saá, Carlos

doi:10.1002/chin.201014131

Cited by 2 publications

(2 citation statements)

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“…Scheme illustrates the different pathways, for example, route R 1 , R 2 , R 3 , and R 4 for alkyne→vinylidene tautomerization . Route R 1 involves direct 1,2‐hydride transfer, which was initially proposed by Dixneuf and Bruneau and later supported by isotope labeling experiments for alcohol addition to alkynes . To map the profile of route R 1 , we performed the PES (potential energy surface) scan by transferring the H 2 atom from C α to C β in 9 III (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Solvent‐Promoted Regio‐ and Stereoselectivity in Ru‐Catalyzed Hydrocarboxylation of Terminal Alkynes: A DFT Study

Maity

Koley

2017

ChemCatChem

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DFT calculations at the M06L‐D3(SMD)/LANL2TZ(f)/6‐311+G(d,p)//M06L/LANL2DZ/6‐31G(d)* level were performed to explore the mechanism, solvent effect, and origin of selectivity in the hydrocarboxylation of terminal alkynes catalyzed by (PCy3)2(CO)RuHCl. This catalytic system offers a unique example in which selectivity in enol‐ester synthesis is controlled in presence of different solvent media under mild reaction conditions. In CH2Cl2 solvent the regioselective gem‐enol‐ester (Pg) was preferred, whereas stereoselective Z‐enol‐ester (PZ) was observed exclusively in THF medium. We have unraveled the complete catalytic mechanism involving the following steps: a) alkyne coordination with subsequent nucleophilic attack and, finally, b) product elimination leading to the Markovnikov product Pg in both solvent media. Herein, the rate‐limiting nucleophilic attack step requires an activation barrier of 20.5 (21.0) kcal mol−1, which is 5.7 (5.6) kcal mol−1 lower than the crucial vinylidene formation step encountered for anti‐Markovnikov addition. Interestingly, a new reaction avenue unfolds under explicit THF medium, in which the inherent coordinating nature of the solvent becomes effective in altering the product regioselectivity. Under such an event, a highly facile ligandassisted proton shuttle (LAPS) mechanism is propagated, leading to vinylidene complex 11A. This intriguing mechanistic scenario facilitates favorably furnishing the PZ product rather than the Pg isomer by 4.3 kcal mol−1.

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Section: Resultsmentioning

confidence: 99%

Solvent‐Promoted Regio‐ and Stereoselectivity in Ru‐Catalyzed Hydrocarboxylation of Terminal Alkynes: A DFT Study

Maity

Koley

2017

ChemCatChem

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“…7 In addition, Ru-catalyzed cyclo-isomerization of aromatic homo-and bis-homopropargylic alcohols was reported to afford benzofurans and isochromenes. 8 It was also reported that the chroman-2-ylidene complexes could be prepared through carbyne intermediate. 9 It is therefore useful to develop efficient methods to generate polycyclic products containing chromane skeleton as precursors for the synthesis of natural products.…”

Section: Introductionmentioning

confidence: 98%

Intramolecular Cyclization of Arylalkynes with C‐O Bond Formation on Ruthenium Complexes

Chang

Tsai

et al. 2013

J Chinese Chemical Soc

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Cyclization of terminal arylalkynes containing aldehyde (1a), ketone (1b-c) or hydroxyl (6a-c) functionality on the aryl ring induced by ruthenium complex is investigated. For the reaction of Cp(PPh 3 ) 2 RuCl with o-ethynyl benzaldehyde 1a, a vinylidene intermediate was formed which is followed by a carbonyl attack to give 2a. However, for 1b-c, with a ketone replacing the aldehyde group, isobenzofuryl carbene complexes (4b-c) were formed as the major products along with the isochromene carbene complexes (2b-c) as the minor products. For three o-enynyl phenol compounds 6a-c with different substituents on the aryl ring, the reactions take place at the triple bond first giving vinylidene intermediates which undergo facile intramolecular cyclization to yield the cyclic oxocarbene complexes 7a-c in excellent yields. Modification of various substituents at Cb of the carbene ligand of 7 by the use of different alkyl halides can be readily achieved under mild condition. For the chromane ring derivatives 11, the two allyl groups underwent ring closing metathesis reaction in the presence of Grubb's catalyst and yielded the tricyclic product 12. These chemical reactions and their mechanisms are corroborated by structure determinations of two ruthenium complexes using single crystal X-ray diffraction analysis.

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ChemInform Abstract: Cycloisomerization of Aromatic Homo‐ and Bis‐homopropargylic Alcohols via Catalytic Ru Vinylidenes: Formation of Benzofurans and Isochromenes.

Cited by 2 publications

References 1 publication

Solvent‐Promoted Regio‐ and Stereoselectivity in Ru‐Catalyzed Hydrocarboxylation of Terminal Alkynes: A DFT Study

Solvent‐Promoted Regio‐ and Stereoselectivity in Ru‐Catalyzed Hydrocarboxylation of Terminal Alkynes: A DFT Study

Intramolecular Cyclization of Arylalkynes with C‐O Bond Formation on Ruthenium Complexes

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