Further Observations on the Formation of Naphthalenes by Double Insertion of Acetylenes into Benzyne−Nickel(0) Complexes

Bennett, Martin A.; Wenger, Eric

doi:10.1021/om9607210

Cited by 37 publications

(23 citation statements)

References 13 publications

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“…This conclusion is supported by the observation that an excess of octa-1,7-diyne, HCC(CH 2 ) 4 CCH, reacts with 41 to give only the tetrahydroanthracene 53 (Scheme 10), no disubstituted naphthalene of general formula C 10 H 6 (C 4 H 8 CCH) 2 being observed [60].…”

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 81%

“…Only in the reaction of DMAD with [Ni(h 2 -C 6 H 4 )(dcpe)] could the mono-insertion product [Ni{o-C 6 H 4 C(CO 2 Me)C(CO 2 Me)-kC,C}(dcpe)] (30) be isolated. Its relative stability may arise from electron delocalization into the carboxylate group on the b-C-atom, giving rise to a resonance contribution from a dipolar NiÀcarbene structure [58] [60], as illustrated in Scheme 5.…”

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

“…The product, [Ni{C(CO 2 Me)C(CO 2 -Me)C 10 H 6 CF 2 CF 2 -kC,C}(dcpe)] (35), results from insertion of the alkyne into the NiÀAr bond of the first insertion product, [Ni(o-C 10 H 6 CF 2 CF 2 -kC,C)(dcpe)] (34) [61]. The nickelaindene complex [Ni{o-C 6 H 4 C(CO 2 Me)C(CO 2 Me)-kC,C}(dcpe)] (30) reacts cleanly with the electrophilic alkynes YCCCO 2 R (Y H, Me, R Me; Y Ph, REt) to give exclusively the naphthalene-1,2,3-triesters 31 ± 33 (Scheme 5; Table 3, Entries 5 ± 7) (see [60] and Exper. Part).…”

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

“…The regioselectivity behaviour is, however, in marked contrast with that observed for insertion into the phosphanickelacycles 6a,b (Section 2), where PhCCCO 2 Et (exclusively) and MeCCCO Table 3, Entry 12), the regiochemistry for each insertion placing the carboxylate group adjacent to the metal atom; however, the isolated organic product 38 is derived from protonation of the intermediate nickelacycle rather than reductive elimination. In this context, the double-insertion reactions of HCCCO 2 R (R Me, t Bu), MeCCCO 2 Me, or PhCCCO 2 Et with the benzyne complexes [Ni(h 2 -C 6 H 2 X 2 )(PEt 3 ) 2 ] (X H (41a), F (41b)) are of particular interest (Scheme 9) [30] [60]. The initial insertions give the reactive five-membered intermediates 42 ± 45 having the carboxylate group adjacent to Ni.…”

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

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Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

Bennett

Macgregor

Wenger

2001

HCA

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In memoriam Professor Luigi M. Venanzi, who contributed so much to coordination and organometallic chemistryAlthough the insertion of alkynes into transition-metalÀcarbon bonds plays an important role in synthesis, the regioselectivities observed with unsymmetric alkynes have usually been interpreted on the basis of steric effects. In this perspective paper, we review the available data for such reactions with nickelacycles and present the results of some preliminary theoretical (DFT) calculations. These suggest that, even for unactivated alkynes, the regiochemistry may also be controlled by electronic factors such as frontier-orbital interactions between the triple-bond of the alkyne and the polarized metalÀcarbon bond.1. Introduction. ± The insertion of an unsaturated molecule into a metalÀcarbon (MÀC) bond is a fundamental reaction in organometallic chemistry that has been exploited in both organic syntheses and industrial processes. Detailed experimental studies have been carried out on alkene and CO insertions [1] [2], and these have been underpinned by extensive theoretical investigations [3]. Alkyne insertion reactions have also received considerable attention, especially in the context of transition-metalcatalysed cyclotrimerization and oligomerization reactions [4 ± 8]. The insertion of an alkyne into the MÀC s-bond of a metallacycle provides a synthetically useful process, because cyclometallated compounds can often be prepared directly by cleavage of a CÀH bond close to a suitable donor atom [9 ± 11]. In particular, alkyne reactions with palladacycles have found wide application in the synthesis of important polycyclic and heterocyclic molecules [12 ± 18]; a stoichiometric process based on cyclomanganated complexes derived from aromatic ketones [19] [20] and a process based on a-tetralone catalysed by [RuH 2 (CO)(PPh 3 ) 3 ] [21] have also been reported.If unsymmetric alkynes are to be used in such reactions, good regioselectivity or even complete regiocontrol is essential. Although several mechanistic studies of the insertions of alkynes into NiÀC and PdÀC bonds have been reported [22 ± 27], little is known about the factors governing the regiochemistry of alkyne insertions into MÀC bonds. Both electronic and steric effects have been invoked to explain the regioselectivities observed for the insertions of alkynes into PdÀaryl bonds, but, although the latter argument is generally preferred, neither could satisfactorily be applied in all cases [16] [17] [28]. For example, two investigations of the insertions of

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Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 81%

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

Section: Insertion Reactions Of Nickelacycles Containingmentioning

confidence: 99%

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Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

Bennett

Macgregor

Wenger

2001

HCA

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“…Thus, complex 44 undergoes the insertion of two molecules of 3-hexyne to afford 43 in good yield, and double insertion of the asymmetric alkyne t-butylacetylene into complex 44 yields naphthalene 45 with a high regioselectivity attributed to steric factors. Interestingly, the reaction of 44 with the more electron-deficient alkyne hexafluoro-2-butyne leads to a mixture of 46, 47 and 48 [28,29]; phenanthrene 46 might be formed by insertion of a second aryne molecule into an intermediate nickelacycle. 116 E. Guitián et al…”

Section: Aryne Complexes Of Late Transition Metalsmentioning

confidence: 99%

Palladium-Catalyzed Cycloaddition Reactions of Arynes

Guitián

Pérez

Peña

2005

Topics in Organometallic Chemistry

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Cotrimerizations of Acetylenic Compounds

et al. 2007

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The cyclotrimerization of acetylenic compounds is a useful method for the construction of three new bonds in a one‐step process. Although symmetry‐allowed, there is a paucity of examples of purely thermal [2+2+2] cycloadditions. The first example reported was in 1866, which was the cyclization of acetylene to benzene. High temperatures are required for this reaction and a mixture of products is formed. In 1948, Reppe discovered the first transition‐metal catalyzed version of this reaction in which nickel was used and substituted benzenes were formed. Since then catalysts based on transition metals, lanthanides, actinide, and aluminum have been developed for the cycloaddition of substituted alkynes to benzene derivatives. Many compounds can take part in the cyclization reactions to give four‐, five‐,six, or eight membered rings. Many of these reactions have found many applications in organic synthesis This chapter is devoted to early to late transition metal‐mediated cotrimerization of acetylenic compounds directed towards organic synthesis. It addresses the scope and generality of the reaction, as well as the current state of the art, with regard to region‐and stereoselectivities. In the context of selectivity, a mechanistic overview is provided. Inter‐and intramolecular versions of the cyclizations are presented with an emphasis on applications in synthesis. The literature up to mid‐2004 is covered.

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Further Observations on the Formation of Naphthalenes by Double Insertion of Acetylenes into Benzyne−Nickel(0) Complexes

Cited by 37 publications

References 13 publications

Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

Palladium-Catalyzed Cycloaddition Reactions of Arynes

Cotrimerizations of Acetylenic Compounds

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