Thermodynamic control of regioselectivity in the addition of carbanions to (arene)tricarbonylchromium complexes

Kündig, E. Peter; Desobry, V.; Simmons, Dana P.; Wenger, Eric

doi:10.1021/ja00187a039

Cited by 73 publications

(28 citation statements)

References 1 publication

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“…unsuccessful due to the instability of these products. The 'H and I3c NMR data of the addition products [3] and [4] are listed in Tables 1 and 2. For the purpose of identification, the site of hydride addition has been designated position one, and numbering proceeds around the ring, so that the phenoxy group is the lowest possible number.…”

Section: Resultsmentioning

confidence: 99%

“…anions to organometallic complexes has led to novel routes to Addition of carbanions, hydrides, phosphorus and nitrogen the functionalization of aroma-tic compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). It is well known that the complexation of a metal moiety, such as (C0)3Cr, (CO),Mn+, ( c~H~) F~~+ , Or CpFe+ to an aromatic system activates the arene ring towards nucleophilic addition reactions .…”

Section: Introductionmentioning

confidence: 99%

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Nucleophilic addition to di- and poly-iron arene complex cations

Abd‐El‐Aziz¹,

Armstrong²,

Bernardin³

et al. 1996

Can. J. Chem.

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Abstract:Hydride and cyanide addition to a series of di-and polycyclopentadienyliron arene complex cations with etheric bridges is described. Reaction of the di-iron complexes with sodium borohydride resulted in the formation of a number of adducts. p-Methyl-and o,o-dimethylphenoxybenzene cyclopentadienyliron complexes were used as models in this study to allow for the characterization of the analagous di-iron complexes. The use of HH COSY and CH COSY NMR techniques enabled us to identify the isomeric nature of these adducts. The hydride addition results indicated that the etheric substituent had the predominant effect over the methyl group, leading to a higher addition ratio to the meta-, followed by the ortho-, then the para-positions. It was also clear that in the di-iron system, the hydride addition to each complexed arene ring took place independently. The addition of the cyanide anion to di-and poly-iron arene systems was more selective than that of the hydride anion. Reaction of sodium cyanide with p-methyl-or o-methyl-substituted arene complexes led to the formation of one adduct, with the cyanide being added to the meta position to the etheric bridges. However, cyanide addition to the di-iron complex, with a methyl substituent attached at the meta position of each complexed arene, led to the formation of a mixture of adducts. Cyanide addition to the poly-iron system withp-substituted arenes proved to be very selective, allowing for the formation of one adduct.Oxidative demetallation with 2,3-dichloro-5,6-dicyano-1.4-benzoquinone (DDQ) produced the uncomplexed polyaromatic ethers with cyano groups in a very good yield. des Cthers polyaromatiques non complexCs portant des groupes cyano.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nucleophilic addition to di- and poly-iron arene complex cations

Abd‐El‐Aziz¹,

Armstrong²,

Bernardin³

et al. 1996

Can. J. Chem.

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“…The data show that equilibration is occurring within minutes at -78 °C, and the product distribution does not further change upon warming to 20 °C. The effect of added HMPA was also observed in halide substitution (addition/elimination) and clearly established during addition to simple arenes [35,116]. With the less sterically demanding anion, LiCH 2 CN, addition is incomplete after 22 h at -78 °C, and favored at C-3 (82:18 for C-3/C-5).…”

Section: Regioselectivitymentioning

confidence: 83%

“…Reversibility in the addition of the carbanion also depends on the structure of the arene ligand, the nature of the counterion and the solvent [35]. A lithium counterion allows faster equilibration compared to potassium, whereas addition of HMPA slows down equilibration up to fourfold in some cases.…”

Section: S N Ar Addition/elimination Ipso Substitutionmentioning

confidence: 99%

“…The addition of synthetically-interesting carbanions to the typical arene ligand, especially those bearing electron-donating substituents, can be reversible at rates comparable to the rate of addition: it is not always obvious whether to assume kinetic or thermodynamic control [35,[106][107][108][109]. However, correlations have been suggested which allow prediction or rationalization of regioselectivity with a modest degree of confidence.…”

Section: Regioselectivitymentioning

confidence: 99%

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(Arene)Cr(CO)3 Complexes: Aromatic Nucleophilic Substitution

Semmelhack

Chlenov

2004

Topics in Organometallic Chemistry

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Transition metals coordinated to the pi system of arenes function as strong electronwithdrawing groups and favor nucleophilic addition to the arene to give cyclohexadienyl-metal complexes. The regioselectivity of addition is influenced in subtle and indirect ways, compared to the powerful effect on both reactivity and regioselectivity of electron-withdrawing groups attached to the sigma bond system of the arene. The intermediate cyclohexadienyl complexes can be processed in several ways, leading to several distinct synthesis methods. Useful reactivity is known for several metal systems and each is discussed for specific reaction types. The presence of a fluoro or chloro substituent on the arene allows an effective analog of classical S N Ar reactivity, with a wide range of nucleophiles including simple amines, alkoxides, and carbon anions. Another general process is the addition/protonation protocol, where a hydrogen substituent on the arene is replaced by a nucleophile. This opens new questions of regioselectivity since the typical arene ligand has several hydrogens which are candidates for substitution. The formation of five-and six-membered rings by both general mechanisms are known. Less general indirect mechanisms (e.g., tele substitution) have also been defined.

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