Deuterium methyllithium

It was predicted, a priori, that isocomene could be formed simply by treating 4 with methyllithium, followed by exposure of the resultant tertiary carbinol to acid.2b However, many attempts to effect the addition of a variety of nucleophilic methyl derivatives to ketone 4 were unsuccessful. It was revealed by deuterium quenching experiments that ketone 4 undergoes ready enolization in the presence of nucleophilic methyl derivatives. Despite its hindered nature, however, the ketone carbonyl in 4 reacts with methylenetri-... 

The IR spectra of methyllithium exhibited two C—H bending vibrational modes at 1480 and 1427 cm . Their assignment was again substantiated by significant isotopic shifts to 1100 and 1043 cm in the deuterium compound (Table 1). Only one weak band was observed for ethyllithium in the C—H deformation region at 1450 cm . Moreover, a new sharp peak was detected at 1385 cm and ascribed to the C—H symmetrical bending mode of CH3. Its absence in the IR spectrum of methyllithium is a further indication that free methyl groups exist only in ethyllithium. 

Bands, which do shift upon lithium substitution, were found in both compounds below 600 cm . The two absorption bands observed near 500 cm in methyllithium appeared at much higher wavenumbers in the corresponding Li compound. Most of the shifts observed upon Li substitution (Table 1) are smaller than the characteristic shifts for harmonic C—Li bonds (about 26 cm for bands near 500 cm ) , as expected since they represent complex vibrational modes. Furthermore, aU of these signals are significantly shifted upon deuterium substitution, which indicates that they involve the motion of hydrogen as well as lithium (Table 1) . ... 

Ring protons of 1,2,3-thiadiazoles are known to undergo rapid deuterium exchange under basic conditions, yet to date there have been no published estimates or experiments to determine the pA of these protons. Few attempts have even been made to metalate and alkylate this heterocycle. One study <85S945> found that metalation of 5-phenyl-1,2,3-thiadiazole (25) with methyllithium gives 4-lithio-5-phenyl-l,2,3-thiadiazole, which is stable and reacts with aldehydes and ketones in high yields (Equation (11)). Also, treatment of 4-phenyl-1,2,3-thiadiazole with lithium diisopropylamide, in the presence of TMS-Cl, affords 4-phenyl-5-trimethylsilyl-1,2,3-thiadiazole. 

Bis(phenylselanyl)methyllithiums 429 (R = H) are stable till 0 °C and were initially trapped with deuterium oxide, methyl iodide and benzophenone639. a-Substituted organolithium intermediate 429 (R = Me, w-CgH ), prepared with LiTMP in THF/HMPA at — 20 °C, reacted with alkyl bromides, ethylene oxide and benzaldehyde to give products 430 in good yields (Scheme 113)640. Bis(methylselanyl)methyllithiums 431 have been allowed to react with different electrophiles to afford products 432 (Scheme 113)640. Alkylated products have been deprotected with mercury(II) chloride or copper(II) chloride/copper(II) oxide, and by oxidation with hydrogen peroxide or benzeneseleninic anhydride644. Deprotection of selenoacetals to ketones can also be performed with sulfuric acid645. 

When a silyl enol ether is the trimethylsilyl derivative (Me3Si-0-C=C), treatment with methyllithium will regenerate the hthium enolate anion and the volatile trimethylsilane (Me3SiH). The enolate anion can be used in the usual reactions. In a similar reaction, a trimethylsilyl enol ether was treated with Cp2Zr (from Cp2ZrCl2/2 BuLiArHE/-78°C), and subsequent quenching with D2O led to incorporation of deuterium at the vinyl carbon (C=C-D). ... 

Very recently an isotopic finger print method which rests on deuterium-induced isotope shifts for Li resonances has been proposed by Gunther and exemplified with applications from the aggregation behavior of cyclopropyllithium systems and mixed aggregates formation between methyllithium and lithium salts. By using one- and two-dimensional NMR experiments based on scalar spin-spin coupling and nuclear overhauser effects the structural aspects associated with benzyllithium and the formation of polylithium systems by lithium reduction of biphenylenes have been discussed. 

Reaction of l,2 5,6-di-0-isopropylidene-3-0-triflyl-a-D-glucofuranose with methyllithium gives the corresponding glycal (double bond in the 3,4-position) by an apparent E-2 elimination. However, deuterium labelling experiments suggest the mechanism first involves deprotonation at C-3 followed by a 1,2-hydride shift from C-4->C-3 and hence to product. ... 

At 0 °C, a 2.0 M solution of n-butyllithium (0.11 mol) in pentanes (or the same amount of ethereal methyllithium) is added to phenylacetylene (11 mL, 10 g, 0.10 mol) in diethyl ether (10 mL). A 1.5 M ethereal solution of deuterium chloride,freshly prepared and stored in a Schlenk buret at -25 °C, follows immediately afterward. The solvent is removed by slow distillation through a 20 cm long Widmer column. Short-path distillation of the remainder gives a colorless liquid (93% bp 141-143 °C 1.5523). The infrared... 

In a related reaction but using deuterium instead of tritium, epoxide 354 was treated with the cuprate reagent prepared from in situ generated [ H3]methyllithium and copper(I) cyanide to provide 355 (major isomer, 65% yield), an intermediate in the preparation of L-(25,35)-[4,4,4-2H3]valine l... 

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