Chloride Lithium-Aluminium Double

Trialkylstannylalkyl)phosphonates, R3SnCHR P(0)(0R")2> can be prepared by lithia-tion of the alkylphosphonate followed by reaction with the alkyltin chloride (equation 6-20),56 or by an Arbuzov reaction between an iodomethyltin compound and a phosphite (equation 6-21).57 The activated Sn-C bond will then add to a dipolar double bond, and the phosphonate group can be reduced to CH2PH2 with lithium aluminium hydride. 

Reduction with lithium aluminium hydride-aluminium chloride (3 1) provides a good route from a,(3-unsaturated carbonyl compounds to unsaturated alcohols (or amines), which are difficult to prepare with lithium aluminivun hydride alone because of competing reduction of the carbon-carbon double bond. For example, a,p-unsaturated esters are reduced to allylic alcohols, although diisobutyla-luminium hydride (DIBAL-H) is normally the reagent of choice for this transformation. Reduction of carboxylic amides can sometimes be preferable using AIH3 (7.78). 

The synthesis of buprenorphine has a certain similarity to that of etorphine. After the Diels-Alder reaction of thebaine with methyl vinyl ketone, the double bond is hydrogenated. Then follows a Grignard reaction with t-butyhnagnesium chloride. For modification of the tertiary amine, this is demethylated with cyanogen bromide (von Braun reaction) and treated with cyclopropanecarbonyl chloride. Following reduction with lithium aluminium hydride, the aromatic methoxy-group is finally replaced by nucleophihc substitution under forcing conditions. 

The cuprate-mediated reaction of l-phenoxy-(2i ,7)-octadiene with propylmag-nesium chloride leads to undeca-l,6-diene, which may be selectively oxidised at the terminal double bond in a Wacker oxidation. Further oxidation with sodium hypobromite (haloform reaction) and reduction with lithium aluminium hydride then lead to (5 )-decenol, which can be esterified with acetic anhydride. The alcohol and the acetate are then mixed corresponding to their ratio in the natural pheromone composition. [187]... 

All of these reactions may be repeated starting with methyl (2/ ,3f )-3-hydroxy-2-methylbutanoate (9a) which is obtained, as shown in Scheme 2, by the double deprotonation of methyl 3-hydroxybutanoate (2b) using lithium di-isopropylamide (LDA) to give the alkoxide-enolate (8) and alkylation with a methyl halide in THF at —After reduction with lithium aluminium hydride, tosyla-tion of the alcohol group and nucleophilic attack by lithium chloride, the (2f ,3f )-l-chloro-2-methyl-3-butanol (10) is available for the sequential metallation reactions and conversion to 1,4-diols or lactones. 

The disordered aluminium hydroxide and the chloride of the double hydroxide of lithium and aluminium (LADH-Cl) synthesized on the basis of the former species are capable of extraction lithium selectively from complex salt chloride systems while the well crystalline compounds possess these properties to a lesser extent. The formation of LADH-Cl from aluminium hydroxide, desorption and sorption of lithium chloride are connected with the processes of its intercalation-deintercalation in the layered matrix. These processes can be described by the following scheme ... 

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