Di-tert-butylcarbene: the low temperature photochemistry of di-tert-butyldiazomethane

Gano, James E.; Wettach, Richard H.; Platz, Matthew S.; Senthilnathan, V. P.

doi:10.1021/ja00372a045

Cited by 44 publications

(26 citation statements)

References 2 publications

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“…[21,24] A metallacyclobutane, [M][CH(tBu)CMe 2 CH 2 ], formed by intramolecular insertion of the carbene moiety into a b CÀH bond could be an intermediate in the formation of 11. However, 11 was detected in trace amounts, indicating that rearrangement of the carbenoid species by b-H migration is not a preferred pathway.…”

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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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: 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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“…56 Irradiation of di(tert-butyl)diazomethane (18-N 2 ) in a degassed MTHF glass at 20 K produced the characteristic ESR spectrum of a triplet. The ZFS parameters (D/hc ) 0.689 cm -1 , E/hc ) 0.039 cm -1 ) fully support the assignment of the triplet spectrum as 3 18.…”

Section: Di(tert-butyl)carbenementioning

confidence: 99%

Persistent Triplet Carbenes

Hirai,

Itoh,

Tomioka

2009

Chem. Rev.

144

123

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“…Hydrogenation of the cyclopropyl group of tetrakis(1-methylcyclopropyl)ethylene gives the wrong isomer (an ethylmethyl group is formed instead of trimethyl, sec-butyl instead of tert-butyl) [12], reaction of tetraacetylethylene with excess dimethyltitanium chloride did not give alkene 1 but a derivative of bicyclo[3.3.0]oct-5-ene [13]. It should be mentioned that 1,1,2,2-tetra-tertbutylethane (8) has been prepared by reaction of dibromoditert-butylmethane by treatment with metals like sodium, potassium and magnesium in THF [14]. This result shows already qualitatively, that it is easier to elongate a C,C single bond than a C,C double bond, a not altogether surprising result given the characteristic ir stretching frequencies of both types of bonds.…”

Section: Introductionmentioning

confidence: 99%

“…Recently Ephritikine et al found also some reduction of the keto to a methylene group, when di-tert-butylketone was treated with TiCl 4 /Li [7c]; a carbenoid species was deduced as intermediate by the authors. They have been several attempts to dimerize di-tert-butylcarbene (5), but neither low temperature photolysis of di-tert-butyldiazomethane [8], nor thermal decomposition of di-tert-butyldiazomethane yielding carbene 5 on metal surfaces any dimerization products were obtained [9]. It should be mentioned that several "tied-back" derivatives of alkene 1 such as anti-fenchylidenefenchane (6), have been successfully prepared [2, 10].…”

Section: Introductionmentioning

confidence: 99%

Tetra-tert-butylethylene, fantasy, fake, or reality?

Lenoir¹,

Wattenbach²,

Liebman

2006

Struct Chem

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This paper reviews all recent attempts to prepare tetra-tert-butylethylene. Some of the synthetic pathways approached this molecule very close but failed during the last step. According to recent DFT calculations this alkene should be a stable molecule with a strain energy in the range of 93 kcal/mol. Since all synthetic approaches failed new methodologies have to be developed, that is either synthesis of the perfluoro derivative of this alkene or the reaction of the radical cation or the radical anion of di-tert-butylmethane with the carbene by a crossed beam technique in the gas phase.(2) Di-tert-butyldiisopropylpropylethylene (3) Tri-tert-butylethylethylene (4) Tetraaldehyde (5) Di-tert-butylcarbene (6) anti-fenchylidenefenchane (7) 1,2-Di-tert-butyl-3,3,5,5-tetramethylcyclopentene (8) Tetra-tert-butylethane (9) 1,1-Dimethyl-2-tert-butylcyclopropane

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Di-tert-butylcarbene: the low temperature photochemistry of di-tert-butyldiazomethane

Cited by 44 publications

References 2 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

Persistent Triplet Carbenes

Tetra-tert-butylethylene, fantasy, fake, or reality?

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