Observations on the reductive deoxygenation of aryl and α,β-unsaturated carbonyl compounds with chlorotrimethylsilane and zinc

Banerjee, Ajoy K.; Carrasco, María C.; Frydrych-Houge, Catherine S. V.; Motherwell, William B.

doi:10.1039/c39860001803

Cited by 27 publications

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“…[9] Also, the reductive coupling of aryl and a,b-unsaturated carbonyl compounds by this ZnÀMe 3 SiCl system was shown to proceed via carbenoid species, and not via pinacolic intermediates. [10] These observations demonstrate the complexity of the mechanism of the McMurry reaction; this complexity was not suspected for a long time, as the analogies with the Wittig and Clemmensen reactions were overlooked.…”

Section: Resultsmentioning

confidence: 98%

“…The ZnÀMe 3 SiCl combination was also effective in the reductive coupling of aryl and a,b-unsaturated carbonyl compounds; here again, these reactions were shown to involve carbenoid species and no pinacol-type intermediates. [10] Such involvement of carbenoid species in the reactions of 1 with the MCl 4 /Li(Hg) system would thus explain the formation of 5, after a-H migration, and also that of 3. The mechanism would be similar to that of the reductive coupling of ketones by means of low-valent niobium, [11] molybdenum, or tungsten compounds (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

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Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Villiers

Ephritikhine

2001

Chem. Eur. J.

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Analysis of the products of the reactions of ketones R2CO (R = Me, Et, iPr, tBu) with the MCl4/Li(Hg) system (M = U, Ti) at 20 degrees C revealed significant differences. For R = Me, the reaction proceeded exclusively (M = U) or preferentially (M = Ti) via a metallopinacol intermediate resulting from dimerization of ketyl radicals. Pinacol was liberated by hydrolysis, and tetramethylethylene was obtained after further reduction at 65 degrees C. For R=iPr, formation of iPr2C=CiPr2 as the only coupling product, the nonproduction of this alkene by reduction of the uranium pinacolate [U]-OCR2CR2O-[U] (R= iPr) at 20 degrees C, and the instability of the corresponding titanium pinacolate towards rupture of the pinacolic C-C bond indicated that reductive coupling of iPr2CO did not proceed by dimerization of ketyl radicals. Formation of 2,4-dimethyl-2-pentene was in favor of a carbenoid intermediate resulting from deoxygenative reduction of the ketyl. These results revealed that for sterically hindered ketones, McMurry reactions can be viewed as Wittig-like olefination reactions. For R=tBu, no coupling product was obtained and the alkane tBu2CH2 was the major product. The involvement of the carbenoid species [M]=CtBu2 was confirmed by its trapping with H2O, leading to tBu2CH2, and with the aldehydes RCHO, giving the cross-coupling products tBu2C=C(R)H (R = Me, tBu). Therefore, in the case of severely congested ketones, McMurry reactions present strong similarities to the Clemmensen reduction of ketones, owing to the involvement in both reactions of carbenoid species which exhibit similar reactivity.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Villiers

Ephritikhine

2001

Chem. Eur. J.

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“…6 The reductive dimerization of isoquinoline has also been observed in the presence of Li or Mg and TMSCl. 7…”

Section: Methodsmentioning

confidence: 93%

“…6 The reductive dimerization of isoquinoline has also been observed in the presence of Li or Mg and TMSCl. 7 The optimization of the experimental conditions was undertaken for the synthesis of N,N'-dimethyl-1,2-diphenylethane-1,2-diamine (R=Ph, R'=Me, 2a), the most employed in our group.…”

Section: Methodsmentioning

confidence: 93%

Practical and Efficient Synthesis of C₂ Symmetrical Diamines with Zn/Me₃SiCl

Alexakis

Aujard

Mangeney

1998

Synlett

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C 2 symmetrical diamines are efficiently obtained by reductive coupling of imines with the couple Zn/Me 3 SiCl. This high yielding method is very practical and cheap for large scale preparation.Chiral C 2 symmetrical diamines are among the most promising chiral auxiliaries in asymmetric synthesis. 1 Our group is strongly involved in this field, 2 and new practical methods are needed to prepare, in bulk, a variety of such diamines. Among the various ways of preparation, the pinacol-type coupling of imines seems the most attractive. The use of a low valent metal for such a reductive coupling is known since 1908, 3 and several metals have since been used. 4 Most of them, however, suffer from high cost or practical problems in scaling up, such as filtration and isolation of the desired diamine. Scheme 1The coupling reaction usually affords the useful racemic d,l diamine, the useless meso diamine and variable amounts of reduction material. We present herein a very practical and high yielding method, which is even more efficient when associated with the isomerization of the meso diamine into the d,l one, as described in the following article.The reductive properties of the cheap metal Zn(0) have been known for a long time, 5 and the combination of Zn and Me 3 SiCl (TMSCl) has been used previously for the coupling of carbonyl compounds. 6 The reductive dimerization of isoquinoline has also been observed in the presence of Li or Mg and TMSCl. 7

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“…The treatment of steroidal conjugated dienones with zinc dust activated by HCl in THF under reflux affords the desired deoxygenative coupling products. 90 The reagent system Zn-TMSCl can be applied to both the coupling of aryl and α,β-unsaturated carbonyl compounds to alkenes, 91 and the McMurrytype coupling of metallocenyl ketones. A very low concentration of HCl must be present to obtain satisfactory results.…”

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confidence: 99%

The McMurry Coupling and Related Reactions

Takeda

Tsubouchi

2013

Organic Reactions

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The McMurry coupling reaction has been recognized as one of the most efficient methods for the synthesis of alkenes from carbonyl compounds. This reaction can be applied to the preparation of various alkenes that are otherwise difficult to prepare. For example, sterically congested tetrasubstituted alkenes as well as medium to large membered rings involving natural products may be accessed via this process. This coupling utilizes various low‐valent titanium reagents generated by the reduction of titanium (III or IV) chloride with K, Zn, LiAlH 4 , C 8 K, amongst others. Furthermore, a variety of low‐valent metal species other than titanium, including aluminum, zirconium, niobium, molybdenum, indium, tungsten, and samarium, have also been found to promote the reductive coupling of carbonyl compounds. The scope and limitations of these reagent systems are reviewed in this chapter, together with the stereochemistry and reaction mechanism. This reaction is categorized into four coupling modes: i) homocoupling giving symmetrical alkenes, ii) mixed coupling giving unsymmetrical alkenes, iii) intramolecular coupling giving cycloalkenes, and iv) tandem coupling giving cyclic polyenes. Characteristics of these reaction modes are described briefly. A selection of synthetic applications are reviewed, including examples of the preparation of sterically congested and strained alkenes, medium to large‐ring compounds, biologically active targets, as well as substrates applicable in material science. Experimental conditions used for this versatile process are summarized to assist the choice of suitable conditions.

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Observations on the reductive deoxygenation of aryl and α,β-unsaturated carbonyl compounds with chlorotrimethylsilane and zinc

Cited by 27 publications

References 0 publications

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Practical and Efficient Synthesis of C₂ Symmetrical Diamines with Zn/Me₃SiCl

The McMurry Coupling and Related Reactions

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Observations on the reductive deoxygenation of aryl and α,β-unsaturated carbonyl compounds with chlorotrimethylsilane and zinc

Cited by 27 publications

References 0 publications

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Practical and Efficient Synthesis of C2 Symmetrical Diamines with Zn/Me3SiCl

The McMurry Coupling and Related Reactions

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Practical and Efficient Synthesis of C₂ Symmetrical Diamines with Zn/Me₃SiCl