Aluminum, lithium complexes ethyls

R)-aluminum-lithium-BINOL complex (0.024 g, 0.04 mmol) was dissolved in toluene (0.4 ml), and to this solution was added dimethyl phosphite (0.044 g, 0.4 mmol) at room temperature the mixture was stirred for 30 min. Benzaldehyde (0.042 g, 0.4 mmol) was then added at -40°C. After having been stirred for 51 h at -40°C, the reaction mixture was treated with 1 N hydrochloric acid (1.0 ml) and extracted with ethyl acetate (3 x 10 ml). The combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica, 20% acetone/hexane) to give the diethyl (S)-a-hydroxybenzylphosphonate (78 mg, 90%) with 85% enantiomeric excess as a colorless solid of mp 86 to 87°C. 

Although the Michael addition of metal ynolates to a,/ -unsaturated carbonyl compounds is expected to give six-membered cycloadducts, 1,2-addition to carbonyl groups usually precedes 1,4-addition. The cycloaddition of the lithium-aluminum ate complex of silyl-substimted ynolate 112 with ethyl benzylideneacetoacetate (113), which is doubly activated by the ester and keto functions, gives the y-lactone 114 via a [4 4- 2] type cycloaddition (equation 46). Diethyl benzylidenemalonate (115) affords the uncyclized ketene 116 by reaction with 112 (equation 47). This could be taken as evidence for a stepwise mechanism for equation 46. ... 

A slightly more complex Scheme is required for preparation of an antihistaminic agent bearing a secondary amine, e. g., tofenacin (32). In the synthesis of tofenacin, alkylation of the benzhydrol (29) with ethyl bromoacetate affords the alkoxy ester (30) saponification followed by conversion to the methylamide gives (31), which is reduced with lithium aluminum hydride to complete the synthesis of 32. 10... 

Rhinebarger et al. [35] and Eyring et al. [36,37] have used lithium-7 nuclear magnetic resonance (NMR) chemical shift data to determine the stability constants for crown-ether complexes of Li+ in two IL systems consisting of 55/45 mole% N-butylpyridinium chloride-aluminum chloride and l-ethyl-3-methyl-imidazolium chloride-aluminum chloride. The stability constants for... 

With the purpose of employing a more soluble form of complexed lithium hydride in such a process, Ziegler and Gellert heated ethylene in ether under pressure at 120-140 °C with LAH, which had been prepared for the first time by Schlesinger and coworkers. To Ziegler s gratification LAH was smoothly converted into lithium tetraethylaluminate (10), which could be isolated in high yield as a crystalline adduct. As proof of structure, the same adduct was also synthesized by the admixture of the lithium and aluminum ethyl derivatives in a 1 1 ratio (Scheme 2). This study represents the first authenticated instance of hydroalumination. 

Hydroxymethyl-1,4-benzodioxin (137) obtained in 80% yield by reduction of ethyl 1,4-benzo-dioxin-2-carboxylate (39) with lithium aluminum hydride in refluxing ether <91TL5525> reacted with zinc azide bis-pyridine complex under Mitsunobu conditions (triphenylphosphine, diisopropyl azodicarboxylate) to yield exclusively compound (138) in 75% yield. Otherwise, (137) was first reacted with zinc iodide under the same conditions until complete transformation of the starting material into the mixture of regioisomers (139) and (140) excess of dry piperidine was then added to the crude reaction medium to yield the alkenic analogue (141) of Piperoxan <89TL1637>. 

Addition of an ethyl group at Cis is a much more complex proposition. The scheme for preparing the 16/3-ethyl derivative begins with Knoevenagel condensation of DHEA acetate (8-1) with acetaldehyde and base to afford the ethylidene derivative 8-2 (Scheme 4.8a). Catalytic reduction adds hydrogen from the bottom side to give 8-3. The carbonyl at C17 is then reduced with lithium aluminum hydride the acetate is also reduced in the process. Reaction with... 

Lithium aluminum hydride reacts violently with water, and therefore reductions with lithium aluminum hydride must be carried out in anhydrous solutions, usually in anhydrous ether. (Ethyl acetate is added cautiously after the reaction is over to decompose excess LiAIH4 then water is added to decompose the aluminum complex.)... 

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