Aluminum hydrides sources

Nickel catalysts promote the hydroalumination of alkenes using trialkylalanes R3AI and dialkylalanes such as BU2AIH as the aluminum hydride sources [9, 29, 30, 33]. However, exhaustive studies of the range of substrates capable of hydroalumination with these reagents has not been carried out. Linear terminal alkenes like 1-octene react quantitatively with BU3AI at 0°C within 1-2 h in the presence of catalytic amounts of Ni(COD)2 [30]. Internal double bonds are inert under these conditions, whereas with 1,5-hexadiene cycHzation occurs. 

Sodium borohydride and lithium aluminum hydride react with carbonyl compounds in much the same way that Grignard reagents do except that they function as hydride donors rather than as carbanion sources Figure 15 2 outlines the general mechanism for the sodium borohydride reduction of an aldehyde or ketone (R2C=0) Two points are especially important about this process... 

CgH BiBr2, and diphenylbromobismuthine [39248-62-9] C22H2QBiBr, respectively, with lithium aluminum hydride or sodium borohydride at low temperatures yielded only black polymeric substances of empirical formula C H Bi (33). It has been claimed (34) that dimethylbismuthine and diphenylbismuthine can be used as cocatalysts for the polymerisation of ethylene (qv), propylene (qv), and 1,3-butadiene. The source of these bismuthines, however, was not mentioned. 

The alkyl methacrylate monomers were available from various sources. Isobutyl methacrylate (IBMA) (Rohm and Haas) and t-butyl methacrylate (TBMA) (Rohm Tech) may be purified first by distillation from CaH, followed by distillation from trialkyl aluminum reagents as described in detail earlier (20,21). In particular, t-butyl methacrylate (b.pt. 150°C) was successfully purified by distillation, from triethyl aluminum containing small amounts of diisobutyl aluminum hydride. The trialkyl aluminum and dialkyl aluminum hydride reagents were obtained from the Ethyl Corporation as 25 weight percent solutions in hexane. The initiator, -butyllithium, was obtained from the Lithco Division of FMC, and analyzed by the Gilman "double titration" (22). 

Chlorobis(ti5-cyclopentadienyl)hydridozirconium was prepared by lithium aluminum hydride reduction of the dichloro compound using the procedure of Buchwald and co-workers.4 When carried out using chlorobis(n5-cyclopentadienyl)-hydridozirconium obtained from a commercial source, the procedure afforded only a 28% yield of final product. 

D-Ribonolactone is a convenient source of chiral cyclopentenones, acyclic structures, and oxacyclic systems, useful intermediates for the synthesis of biologically important molecules. Cyclopentenones derived from ribono-lactone have been employed for the synthesis of prostanoids and carbocyclic nucleosides. The cyclopentenone 280 was synthesized (265) from 2,3-0-cyclohexylidene-D-ribono-1,4-lactone (16b) by a threestep synthesis that involves successive periodate oxidation, glycosylation of the lactol with 2-propanol to give 279, and treatment of 279 with lithium dimethyl methyl-phosphonate. The enantiomer of 280 was prepared from D-mannose by converting it to the corresponding lactone, which was selectively protected at HO-2, HO-3 by acetalization. Likewise, the isopropylidene derivative 282 was obtained (266) via the intermediate unsaturated lactone 281, prepared from 16a. Reduction of 281 with di-tert-butoxy lithium aluminum hydride, followed by mesylation, gave 282. 

Single-Source-Precursor CVD Alkoxy and SUoxy Aluminum Hydrides... 

The third contribution is particularly devoted to the concept of so-called single source precursors (SSPs). SSPs contain all the atoms of the different elements necessary for the deposition of the desired material in one single molecule. One motivation for using this concept is to simplify the accompanying gas-phase reactions and thus reduce the process parameters to be controlled and optimised. However, SSPs may offer a unique chance of depositing metastable materials that cannot be derived by other methods. M. Veith and S. Mathur provide such an example in their paper entitled Single-Source-Precursor CVD Alkoxy and Siloxy Aluminum Hydrides . 

Tetrahydrofuran, containing less than 0.002% peroxides, supplied by the William A. Mosher, Ph.D. Company, 101 Townsend Road, Newark, Delaware 19711, was used directly. Tetrahydrofuran from other sources may require purification prior to use. Stirring with lithium aluminum hydride or sodium benzophenone ketyl, followed by distillation under an inert atmosphere, is the recommended procedure for removal of water and peroxides (see reference 4, p. 256). 

Addition of hydride to the carbonyl carbon to form an alcohol, or the reverse, changes the oxidation state and so is usually classified separately from other carbonyl reactions. Some of these processes are nevertheless fundamentally similar to the ones we have been considering. Reductions by complex metal hydrides, such as lithium aluminum hydride or sodium borohydride, are additions ofH - (Equation 8.27) the metal hydride ion is simply a convenient source of this extremely basic species. The carbonyl oxygen takes the place of the hydride in coordination with the boron (or aluminum in the case of an alumino-... 

The reagents used in this procedure were obtained from the following sources lithium aluminum hydride, Alfa Inorganics, Inc. thionyl chloride, Matheson Coleman and Bell sodium hydride, Metal Hydrides, Inc. The nitrogen was prepurified. 

Camphorsultam. A dry, 2-L, three-necked, round-bottomed flask is equipped with a 1.5-in egg-shaped Teflon stirring bar, a 250-mL addition funnel, and a 300-mL Soxhlet extraction apparatus equipped with a mineral oil bubbler connected to an inert gas source. The flask is charged with 600 mL of dry tetrahydrofuran (THF) (Note 1) and 6.2 g (0.16 mol) of lithium aluminum hydride (Note 2). Into the 50-mL Soxhlet extraction thimble is placed 35.0 g (0.16 mol) of (-)-(camphorsulfonyl)imine (Note 3) and the reaction mixture is stirred and heated at reflux. After all of the (camphorsulfonyl)imine has been siphoned into the reaction flask (3-4 hr), the mixture is allowed to cool to room temperature. The unreacted lithium aluminum hydride is cautiously hydrolyzed by dropwise addition of 200 mL of 1 N hydrochloric acid via the addition funnel (Note 4). After the hydrolysis is complete the contents of the flask are transferred to a 1-L separatory funnel, the lower, silver-colored aqueous layer is separated, and the upper layer placed in a 1-L Erlenmeyer flask. The aqueous phase... 

The isoquinoline ring undergoes attack by the nucleophilic aluminum hydride anion in much the same manner as the pyridine ring to produce 1,2-dihydroisoquinolines,91,92 although tetrahydroisoquino-lines have been reported as products even though no proton source was apparently present.92 (For a probable mechanism see Section IV,B.) The reduction of isoquinoline A-oxide by lithium aluminum hydride was also reported to yield the 1,2-dihydroisoquinoline.93... 

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