Preparation of lithium amalgam

Alexander, J. B.; Rao, G. Sambasiva

doi:10.1021/ed047p277

Cited by 6 publications

(3 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…THF was dried and deoxygenated over sodium benzophenone ketyl and distilled immediately before use; [D 8 ]THF was dried over Na-K alloy. The organic products were identified by NMR spectroscopy, GC, and GC-MS by comparison with authentic samples, Lithium amalgam (1.05 % Li) was prepared by addition of Li to Hg in boiling p-cymene, [41] and was titrated by flame absorption spectroscopy. TiCl 4 and tBuLi (Aldrich) were used as received; UCl 4 was prepared as described in reference [42].…”

Section: Methodsmentioning

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.

View full text Add to dashboard Cite

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.

show abstract

Section: Methodsmentioning

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.

View full text Add to dashboard Cite

show abstract

“…Synthesis: anti-Tricyclo[4.2.0.0 2,5 ]octa-3,7-diene (anti-TOD) was synthesized by dehalogenation of dichlorocyclobutene [24] (Fluka, purum) by Li amalgam which was prepared in situ according to the procedure of Alexander and Rao. [25] In the workup, the conversion to the silver complex [24] was replaced by purification by preparative gas chromatography at room temperature using b,b'-oxidiproprionitrile (ODP) as a stationary phase.…”

Section: Methodsmentioning

confidence: 99%

The Radical Cation ofanti-Tricyclooctadiene and Its Rearrangement Products

et al. 2000

View full text Add to dashboard Cite

The anti dimer of cyclobutadiene (anti-tricyclo[4.2.0.0(2.5)]octa-3,7-diene, TOD) is subjected to ionization by gamma-irradiation in Freon matrices, pulse radiolysis in hydrocarbon matrices, and photoinduced electron transfer in solution. The resulting species are probed by optical and ESR spectroscopy (solid phase) as well as by CIDNP spectroscopy (solution). Thereby it is found that ionization of anti-TOD invariably leads to spontaneous decay to two products, that is bicyclo[4.2.0]octa-2,4,7-triene (BOT) and 1,4-dihydropentalene (1,4-DHP), whose relative yield strongly depends on the conditions of the experiment. Exploration of the C8H8*+ potential energy surface by the B3LYP/6-31G* density functional method leads to a mechanistic hypothesis for the observed rearrangements which involves a bifurcation between a pathway leading to the simple valence isomer, BOT*+, and another one leading to an unprecedented other valence isomer, the anti form of the bicyclo[3.3.0]octa-2,6-diene-4,8-diyl radical cation (anti-BOD*+). The latter product undergoes a very facile H-shift to yield the radical cation of 1,3a-dihydropentalene (1,3a-DHP*+) which ultimately rearrranges by a further H-shift to the observed product, 1,4-DHP*+.

show abstract

“…The GLC analyses were performed on a Chrompack CP 9002 apparatus equipped with a capillary CP Wax 57 CB column. Sodium amalgam (2.0% Na) was obtained by adding small pieces of sodium to mercury under argon at 20 ЊC; 1.05% lithium amalgam was prepared by addition of Li to Hg in boiling p-cymene, 20…”

Section: Methodsmentioning

confidence: 99%