Efficient Pd‐Catalyzed Allene Synthesis from Alkynes and Aryl Bromides through an Intramolecular Base‐Assisted Deprotonation (iBAD) Mechanism

Nella, Natalie; Parker, Evelyne; Hitce, Julien; Larini, Paolo; Jazzar, Rodolphe; Baudoin, Olivier

doi:10.1002/chem.201403213

Cited by 27 publications

(18 citation statements)

References 55 publications

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“…Possibly, the substrate leading to 3n could experience a β-H elimination upon the carbopalladation step to render an allenyl moiety, as described in other Pd-catalyzed reactions dealing with alkyl-substituted alkynes. 58 , 59 …”

Section: Results and Discussionmentioning

confidence: 99%

Synthesis of Benzofused O- and N-Heterocycles through Cascade Carbopalladation/Cross-Alkylation of Alkynes Involving the C–C Cleavage of Cyclobutanols

et al. 2022

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We report a Pd-catalyzed route to heterocycles bearing a tetrasubstituted alkene fragment. Our approach merges the intramolecular carbopalladation of tethered alkynes with an alkylation step produced by the C–C cleavage of cyclobutanol derivatives. An alkenyl-Pd(II) intermediate has been isolated and characterized by X-ray diffraction studies. Interestingly, the nature of the tethering alkynyl chain influences the E / Z stereochemistry of the alkenyl fragment in the functionalized heterocycles.

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Section: Results and Discussionmentioning

confidence: 99%

Synthesis of Benzofused O- and N-Heterocycles through Cascade Carbopalladation/Cross-Alkylation of Alkynes Involving the C–C Cleavage of Cyclobutanols

et al. 2022

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“…[16] Baudoin and co-workers found that aryl bromides could be reacted with alkynes in the presence of Pd2(dba)3 and an electron rich phosphine ligand 26 (Scheme 7a). [17] Interestingly, the addition of pivalic acid was essential to achieve high conversion to the allene products. Frantz and Neff disclosed a coupling of aryl triflates with alkynes under biphasic reaction conditions with a Pd-BobCat complexin this case the water-soluble dba ligand is extracted into the aqueous phase, preventing deleterious side reactions (Scheme 7b).…”

Section: Scheme 4 Synthesis Of Allenes From β-Halovinyl Ketones and mentioning

confidence: 99%

Synthesis of Allenes by 1,2-Elimination

Armstrong

2020

COC

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Allenes represent an extremely important class of organic molecules, which, as a result of their twisted orthogonal π-systems can possess axial chirality. A wide array of methods for allene synthesis have been reported, such as the substitution of propargylic electrophiles, isomerization of alkynes and sigmatropic rearrangement. An alternative approach for the synthesis of allenes is 1,2-elimination of an appropriately substituted precursor. This mini-review highlights recent examples of 1,2-elimination processes, which target allenes including both polar and radical processes. The main focus is upon how control over the stereospecificity (e.g. syn- or anti-) of the 1,2-elimination process can enable the synthesis of enantioenriched axially chiral allenes. Recent developments in this field are presented including both enantiospecific and catalytic asymmetric methods.

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“…[4][5][6][7] Theoretically, the hydrogen elimination can be divided into two categories according to the hybrid state of the attached carbon atom. Hydrogen elimination from sp 3 -carbon is the most common pattern, and both alkyl and alkenyl palladium complexes [8][9][10][11] can undergo this elimination pathway, affording ole ns and allenes respectively. In contrast, the second hydrogen mode, where the eliminated hydrogen is attached to a sp 2 -carbon (also means β-elimination of vinylic hydrogen from 1 η-allylic palladium) and allene would be generated, has not been reported yet (Fig.…”

Section: Introductionmentioning

confidence: 99%

Palladium-catalyzed allene synthesis enabled by β-hydrogen elimination from sp2-carbon

Zhang

Song

Zhang

et al. 2020

Preprint

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The rational design based on a deep understanding of the present reaction mechanism is an important, viable approach to discover new organic transformations. β-Hydrogen elimination from palladium complexes is an fundamental reaction in palladium catalysis. Normally, the eliminated β-hydrogen has to be attached to a sp3-carbon. We envision that the hydrogen elimination from sp2-carbon is possible by using delicately planed reaction systems, which may offer a new strategy for the preparation of allenes. With this consideration in mind, the palladium-catalyzed cross-coupling of 2,2-diarylvinyl bromides with diazo compounds was realized with a β-vinylic hydrogen elimination from allylic palladium intermediate as the key step. Both aryl diazo carbonyl compounds and N-tosylhydrazones are competent carbene precursors in this reaction. The reaction mechanism was explored by control experiments, KIE studies and DFT calculations

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Efficient Pd‐Catalyzed Allene Synthesis from Alkynes and Aryl Bromides through an Intramolecular Base‐Assisted Deprotonation (iBAD) Mechanism

Cited by 27 publications

References 55 publications

Synthesis of Benzofused O- and N-Heterocycles through Cascade Carbopalladation/Cross-Alkylation of Alkynes Involving the C–C Cleavage of Cyclobutanols

Synthesis of Benzofused O- and N-Heterocycles through Cascade Carbopalladation/Cross-Alkylation of Alkynes Involving the C–C Cleavage of Cyclobutanols

Synthesis of Allenes by 1,2-Elimination

Palladium-catalyzed allene synthesis enabled by β-hydrogen elimination from sp2-carbon

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