Synthesis, structure and reactivity of some (.sigma.-allenyl)- and (.sigma.-prop-2-ynyl)palladium(II) complexes

Elsevier, C. J.; Kleijn, H.; Boersma, J.; Vermeer, P.

doi:10.1021/om00135a015

Cited by 110 publications

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“…As mentioned before,p reviousw orks in this area [17] have includedt he characterization of h 1 -propargyl and/or h 1 -allenyl complexes of Fe, [18] Co, [19] Mo, [18] W, [20] Ru, [21] Pd, [22] and Pt.…”

Section: IIImentioning

confidence: 99%

Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium

Ruiz-Muelle

Oña‐Burgos

Ortuño

et al. 2016

Chemistry A European J

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The synthesis and structural characterization of allenyl titanocene(IV) [TiClCp2 (CH=C=CH2 )] 3 and propargyl titanocene(IV) [TiClCp2 (CH2 -C≡C-(CH2 )4 CH3 )] 9 have been described for the first time. Advanced NMR methods including diffusion NMR methods (diffusion pulsed field gradient stimulated spin echo (PFG-STE) and DOSY) have been applied and established that these organometallics are monomers in THF solution with hydrodynamic radii (from the Stokes-Einstein equation) of 3.5 and 4.1 Å for 3 and 9, respectively. Full (1) H, (13) C, Δ(1) H, and Δ(13) C NMR data are given, and through the analysis of the Ramsey equation, the first electronic insights into these derivatives are provided. In solution, they are involved in their respective metallotropic allenyl-propargyl equilibria that, after quenching experiments with aromatic and aliphatic aldehydes, ketones, and protonating agents, always give the propargyl products P (when carbonyls are employed), or allenyl products A (when a proton source is added) as the major isomers. In all the cases assayed, the ratio of products suggests that the metallotropic equilibrium should be faster than the reactions of 3 and 9 with electrophiles. Indeed, DFT calculations predict lower Gibbs energy barriers for the metallotropic equilibrium, thus confirming dynamic kinetic resolution.

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Section: IIImentioning

confidence: 99%

Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium

Ruiz-Muelle

Oña‐Burgos

Ortuño

et al. 2016

Chemistry A European J

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“…3,4 Transition metal catalysis could provide a solution to this limitation: palladium undergoes stereospecific anti S N 2´ oxidative addition with propargylic electrophiles. 5 This reaction delivers an η 1 -(allenyl)palladium complex ( A , Scheme 1) whose configuration reflects that of the starting material. While (allenyl)palladium complexes can undergo isomerization to η 1 -(propargyl)palladium species ( A→B ), this transformation is also stereospecific.…”

mentioning

confidence: 99%

“…While (allenyl)palladium complexes can undergo isomerization to η 1 -(propargyl)palladium species ( A→B ), this transformation is also stereospecific. 5,6 With appropriately substituted substrates, both the propargyl ( B ) and the allenyl ( A ) palladium complexes are chiral and the fact that they are configurationally stable enables stereospecific cross-couplings. 7 However, the Pd-catalyzed cross-coupling of organometallic reagents and branched propargylic electrophiles generally favors the allene as opposed to the 1,5 enyne product.…”

mentioning

confidence: 99%

Construction of 1,5-Enynes by Stereospecific Pd-Catalyzed Allyl–Propargyl Cross-Couplings

Ardolino

Morken

2012

J. Am. Chem. Soc.

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The palladium-catalyzed cross-coupling of chiral propargyl acetates and allyl boronates delivers chiral 1,5-enynes with excellent levels of chirality transfer and applied across a broad range of substrates.1,5-Enynes are important and versatile synthetic intermediates. In addition to offering differentiated π-systems for selective functionalization, 1,5-enynes can be transformed into a diverse array of cyclic structures. 1 A current challenge to reaction methodology surrounding 1,5-enynes lies in the preparation of these structures in an enantiomerically enriched fashion. Synthesis of 1,5-enynes is commonly accomplished by allylation of propargylic electrophiles, employing either stoichiometric or catalytic Lewis acid activation. 2 While high levels of regiocontrol have been observed in these processes, they appear to proceed through an achiral carbocation intermediate and this feature precludes the transfer of chirality from enantiomerically-enriched starting materials to 1,5-enyne products (Scheme 1, eq. 1). 3,4 Transition metal catalysis could provide a solution to this limitation: palladium undergoes stereospecific anti S N 2´ oxidative addition with propargylic electrophiles. 5 This reaction delivers an η 1 -(allenyl)palladium complex (A, Scheme 1) whose configuration reflects that of the starting material. While (allenyl)palladium complexes can undergo isomerization to η 1 -(propargyl)palladium species (A→B), this transformation is also stereospecific. 5,6 With appropriately substituted substrates, both the propargyl (B) and the allenyl (A) palladium complexes are chiral and the fact that they are configurationally stable enables stereospecific cross-couplings. 7 However, the Pd-catalyzed cross-coupling of organometallic reagents and branched propargylic electrophiles generally favors the allene as opposed to the 1,5 enyne product. 7,8 This regioselectivity likely arises from steric effects; complex A is less hindered than complex B and this leads to allene products on reductive elimination. This reaction manifold renders traditional palladium catalysis ineffective for construction of chiral alkyne-containing compounds from chiral propargylic electrophiles.In contrast to the cross-coupling of alkyl, aryl and vinyl metal reagents, cross-couplings of allyl metal reagents may occur with allyl migration. To exploit this feature, our lab has studied cross-couplings of allyl metal reagents and allylic electrophiles and has found that these reactions appear to occur by an inner sphere 3,3'-reductive elimination. 9,10,11 In the presence of appropriately selected ligands (bidentate, small bite-angle diphosphines), allylallyl cross-couplings occur with excellent levels of regio-and stereocontrol. Along these * Corresponding Authormorken@bc.edu. Supporting Information. Procedures, characterization and spectral data. This material is available free of charge via the Internet at http://pubs.acs.org.The authors declare no competing financial interest. lines, we considered that allyl-propargyl cross-couplings mi...

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“…So, there does not appear to be any incentive for developing Pd-catalyzed benzylalkynyl coupling procedures. [195,196] [ 197,198] Pd(PPh 3 ) 4 (3 mol%) Scheme 3.50 Pd-or Ni-catalyzed aryl-propargyl coupling [195][196][197][198].…”

Section: Benzylated Alkynes Via Pd-catalyzed Alkynyl-benzyl Coupling mentioning

confidence: 99%

“…The Pd-catalyzed reaction of PhZnCl with propargyl acetates and related electrophiles has produced Ph-substituted allenes, which proceeded with inversion at the propargyl carbon atom [195,196] (Eq. (1), Scheme 3.50).…”

Section: Benzylated Alkynes Via Pd-catalyzed Alkynyl-benzyl Coupling mentioning

confidence: 99%

Pd‐Catalyzed Cross‐Coupling with Organometals Containing Zn, Al, Zr, and so on – The Negishi Coupling and Its Recent Advances

Kamada

Kim

et al. 2013

Metal‐Catalyzed Cross‐Coupling Reactions and More

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The Pd-or Ni-catalyzed cross-coupling reactions of organometals containing Zn, Al, Zr, and B as well as related reactions of those containing Mg and several other metals collectively have emerged as arguably the most widely applicable organic skeleton construction method discovered and developed over the past several decades, allowing synthetic chemists to prepare practically all types of organic compounds. In this chapter, some of the seminal and critically important discoveries and early developments in the 1970s as well as their current scope are briefly discussed. Some of the notable discoveries and developments include (i) identification of superior properties of Pd as a critical element for crosscoupling relative to Ni, (ii) the broad scope of Pd-or Ni-catalyzed cross-coupling with respect to metal countercations including Zn, Al, Zr, B, and Mg, (iii) the hydrometallation-Pd-catalyzed cross-coupling sequential processes for selective syntheses of alkenes, dienes, oligoenes, and oligoenynes, (iv) double metal catalysis involving Pd or Ni and added metal compounds containing Zn, In, Li, and others, and (v) realization of high turnover numbers (TONs) (≥10 3 -10 9 ) through the use of chelating phosphines, such as bis-[2-(diphenylphosphino)phenyl] ether (DPEphos) and 1,1 -Bis(diphenylphosphino)ferrocene (dppf).The Zr-catalyzed alkyne carboalumination and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction) have provided efficient and selective routes to (E)-trisubstituted alkenylalanes and 2-substituted chiral alkylalanes, respectively. These reactions provide two additional examples of prototypical transition metal-catalyzed organometallic reactions. Significantly, they can be readily combined with the Pd-or Ni-catalyzed cross-coupling for the synthesis of trisubstituted alkenes embracing a wide variety of natural products, such as terpenoids, carotenoids, and others, as well as various chiral organics including deoxypolypropionates and saturated terpenoids. The Zr-catalyzed alkyne carboalumination has been applied to the synthesis of a large number (>100) of natural products, while the ZACA reaction has been transformed from a mere scientific novelty to a full-fledged asymmetric synthetic method that is catalytic in both transition metal (Zr) and chiral auxiliaries through a series of breakthroughs.

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Synthesis, structure and reactivity of some (.sigma.-allenyl)- and (.sigma.-prop-2-ynyl)palladium(II) complexes

Cited by 110 publications

References 0 publications

Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium

Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium

Construction of 1,5-Enynes by Stereospecific Pd-Catalyzed Allyl–Propargyl Cross-Couplings

Pd‐Catalyzed Cross‐Coupling with Organometals Containing Zn, Al, Zr, and so on – The Negishi Coupling and Its Recent Advances

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