75501-40-5Relevant academic research and scientific papers
Pivaloylmetals (tBu-COM: M=Li, MgX, K) as equilibrium components
Knorr,Boehrer,Schubert,Boehrer
experimental part, p. 7506 - 7515 (2012/07/27)
Short-lived pivaloylmetals, (H3C)3C-COM, were established as the reactive intermediates arising through thermal heterolytic expulsion of O=CtBu2 from the overcrowded metal alkoxides tBuC(=O)-C(-OM)tBu2 (M=MgX, Li, K). In all three cases, this fission step is counteracted by a faster return process, as shown through the trapping of tBu-COM by O=C(tBu)-C(CD3)3 with formation of the deuterated starting alkoxides. If generated in the absence of trapping agents, all three tBu-COM species "dimerize" to give the enediolates MO-C(tBu)=C(tBu)-OM along with O=CtBu2 (2 equiv). A common-component rate depression by surplus O=CtBu2 proves the existence of some free tBu-COM (separated from O=CtBu2); but companion intermediates with the traits of an undissociated complex such as tBu-COM & O=CtBu2 had to be postulated. The slow fission step generating tBu-COMgX in THF levels the overall rates of dimerization, ketone addition, and deuterium incorporation. Formed by much faster fission steps, both tBu-COLi and tBu-COK add very rapidly to ketones and dimerize somewhat slower (but still fairly fast, as shown through trapping of the emerging O=CtBu2 by H3CLi or PhCH2K, respectively). At first sight surprisingly, the rapid fission, return, and dimerization steps combine to very slow overall decay rates of the precursor Li and K alkoxides in the absence of trapping agents: A detailed study revealed that the fast fission step, generating tBu-COLi in THF, is followed by a kinetic partitioning that is heavily biased toward return and against the product-forming dimerization. Both tBu-COLi and tBu-COK form tBu-CH=O with HN(SiMe3)3, but only tBu-COK is basic enough for being protonated by the precursor acyloin tBuC(=O)-C(-OH)tBu2. Copyright
Synthesis and reactivity of benzylic and allylic samarium compounds
Bied,Collin,Kagan
, p. 3877 - 3890 (2007/10/02)
Benzyl and allyl samarium species are prepared by reaction of benzylic or allylic chlorides with SmCp2. They present a wide scope of reactivity towards aldehydes, ketones and acid chlorides.
Reactions of Thermally Generated tert-Butyl and Di(tert-alkyl)ketyl Radicals in Toluene: Cage Effects and Hydrogen Transfer
Lomas, John S.,Briand, Sylvette,Fain, Dominique
, p. 166 - 175 (2007/10/02)
Thermolysis of di(1-adamantyl)-tert-butylmethanol (2a) in toluene at 145-185 deg C gives mainly bibenzyl, di(1-adamantyl) ketone, di(1-adamantyl)methanol, and the cross-product, 1,1-di(1-adamantyl)-2-phenylethanol.In the presence of benzophenone (BP) or benzenethiols as hydrogen-accepting and hydrogen-donating radical scavengers, respectively, the di(1-adamantyl)methanol/di(1-adamantyl) ketone ratio tends to steady values as the scavenger/2a ratio is increased, while the cross-product disappears.At 165 deg C the secondary alcohol minimum is 8percent (BP) and the ketone minimum 11percent (thiol).These represent the contributions of geminate hydrogen atom transfer reactions to the overall yields, i.e., the cage effects.With BP the major cross-product is 1,1,2-tri-phenylethanol.Products from the self- and cross-reactions of benzyl and thiyl radicals are found when thiol is present, the diaryl disulfide predominating at high thiol concentration.In both cases, cross-products resulting from reaction of the tert-butyl radical with the scavenger-derived radical are detected in small amounts, being of greater importance in deuteriated toluene.The tert-butyl radical is considered, therefore, to be less reactive in hydrogen atom abstraction than the 1-adamantyl radical.Cage effects for other di(tert-alkyl)-tert-butylmethanols that thermolyze with exclusive t-Bu-C bond fission have also been measured and the product composition of the scavenger-free reaction interpreted by kinetic simulation based on the steady state approximation.Rate constants for hydrogen abstraction by the tert-butyl radical from toluene are not accurately determined by this procedure but seem, nevertheless, to indicate that the literature value (14.4 M-1s-1 at 48 deg C) is an overestimate. Solvent hydrogen abstraction by the ketyl radical shows a small but well-defined steric effect.
On the Formation and Reactivity of Di-tert-alkyl Substituted Phenylalkenes
Knorr, Rudolf,Lattke, Ernst,Raepple, Edith
, p. 1207 - 1215 (2007/10/02)
Molecular rearrangements occur during the attempted syntheses of α-bromo-β,β-di-tert-alkylstyrenes; the resulting structures are elucidated.A hydrocarbon dimer with allenic structure accompanies the formation of the Grignard reagent from an α-bromostyrene
