E. C. Ashby

Concerning the purity of magnesium and beryllium alkyls and halides prepared by different methods

Abstract Methods for preparing pure magnesium and beryllium alkyls, aryls and halides have been investigated and evaluated. Some previously reported methods were found to produce impure products whereas one method for each class of compounds above was found that produced an unusually pure product. The latter methods are recommended for the preparation of these classes of compounds when high purity products are necessary such as in molecular association or kinetic studies.

Organometallic reaction mechanisms: XVIII. Concerning the nature of the transition state in the reaction of trialkylaluminum compounds with ketones

Et2AlCH2AlEt2 (1) has been used as a mechanistic probe to determine the nature of the transition state in the reaction of two equivalents of a trialkylaluminum compound with a ketone in hydrocarbon solvent.1 was prepared in benzene and the solution composition determined. Low temperature1H NMR data of1 as the mono(diethyl etherate) indicate that the ether oxygen is simultaneously coordinated to both aluminum atoms. The reactions of1 with 4-t-butylcyclohexanone in hydrocarbon solvent were compared to the reactions of triethylaluminium with the same ketone. The results support the importance of a bridging alkyl group described by the formation of a six-centered transition state when two equivalents of a trialkylaluminum compound are allowed to react with a ketone in hydrocarbon solvent. The results also argue against a transition state described by two moles of trialkylaluminum compound complexed to the carbonyl oxygen atom.

Hydrometallation of 1-octene with grignard reagents. Alkylmagnesiums and alkylmagnesium hydrides catalyzed by dicyclopentadienyltitanium dichloride

Abstract The hydrometallation of l-octene by a series of Grignard reagents (EtMgCl, EtMgBr, n-PrMgCl, i-PrMgCl, n-BuMgCl, sec-BuMgCl, iso-BuMgCl, iso-BuMgBr and iso-BuMgI), dialkylmagnesium compounds (Me 2 Mg, Et 2 Mg, n-Pr 2 Mg, iso-Pr 2 Mg, n-Bu 2 Mg, sec-Bu 2 Mg, iso-Bu 2 Mg and t-Bu 2 Mg), alkylmagnesium hydrides (RMgH, where R = Me, Et, T-Bu, Cp and Ph) and magnesium hydrides (MgH 2 , HMgCl and HMgBr) in the presence of 5 mol% dicyclopentadienyltitanium dichloride (Cp 2 TiCl 2 ) in THF has been investigated. The percent yield of octane (produced on hydrolysis of the product) vs. time was plotted for several reactions in order to compare the effect of individual reagents. Most alkylmagnesium compounds with β hydrogen atoms gave primarily the hydrometallation product, although t-Bu 2 Mg produced isomerized starting material. MeMgH gives the best yield of octane on hydrolysis of the reaction mixture. A mechanism is proposed which accounts for all observations.

Evidence for single electron transfer in the reduction of alcoholswith lithium aluminum hydride

Abstract EPR evidence supporting a single electron transfer mechanism in the reduction of secondary and tertiary alcohols to hydrocarbons with LiAlH 4 is presented.

Evidence supporting a single electron transfer pathway in the reduction of aromatic ketones by metal alkoxides. Lithium isopropoxide, an excellent reducing agent for aromatic ketones.

Abstract Reactions of various metal alkoxides with aromatic ketones have been shown to produce radical intermediate. Lithium isopropoxide has been found to be an excellent reducing agent for aromatic ketones and reduces benzophenone at a faster rate than does aluminum isopropoxide.

(endo)-5-(2-haloethyl)-2-norbornene. A new radical probe.

Abstract (endo)-5-(2-haloethyl)-2-norbornenes have been synthesized, and their corresponding radicals generated by reaction with sodium, magnesium, sodium naphthalenide and tri-n-butyltin hydride in the presence of AIBN to produce both straight chain and cyclized products. This probe cyclizes substantially faster than the often used 5-hexenyl halide probes.

Evidence for a single electron transfer mechanism in reactions of lithium diorganocuprates with organic halides

Abstract It has been demonstrated by means of spectroscopic studies involving cyclizable alkyl halides that lithium dimethylcuprate can react with organic halides by a single electron transfer pathway.

EPR evidence for a single electron transfer mechanism in reactions of aromatic ketones with lithium amides

Abstract Direct spectroscopic evidence (EPR) supporting a single electron transfer mechanism in the reaction of lithium amides with aromatic ketones is presented.

Reaction of magnesium hydride with pyridine: Formation of H3Mg2NC5H6, HMgNC5H6 and Mg(NC5H6)2

Abstract The reaction of magnesium hydride with excess pyridine at room temperature results in the formation of soluble bis( N -dihydropyridyl)magnesium which is shown by NMR spectra, to contain 1,2- and 1,4-dihydropyridine groups bound to magnesium. A similar reaction carried out at 60° C has been shown to form bis( N -diihydropyridyl)magnesium containing only 1,4-dihydropyridine groups. Formation of H 3 Mg 2 (NC 5 H 6 ) and HMg(NC 5 H 6 ) are also reported in the controlled reactions of pyridine with magnesium hydride.

The first reported evidence of single electron transfer in the 1,2-addition of primary Grignard reagents to ketones☆

Abstract The first evidence to support the electron transfer nature of the reaction of primary Grignard reagents with aromatic ketones is presented.