Diethoxyaluminum chloride

Dehydration of fi-hydroxy esters. /3-Hydroxy esters are dehydrated to aj3-unsaturated esters in 44-56% yield by treatment with aluminum ethoxide or diethoxyaluminum chloride and then with lithium diisopropylamide. Although the yields are moderate, no /3,7-isomers are formed and, in suitable cases, only the E-isomer is obtained. The reaction is considered to proceed through a P-alanoxy intermediate, which can form a six-membered ring transition state on enolization. 

DEHYDRATION Diethoxyaluminum chloride. Lithium n-propylmercaptide. N-Methyl-N,N -di-r-butylcarbodiimidium tetrafluoroborate. o-Nitrobenzenesulfonyl chloride. Potassium acetate. Thiobenzoyl chloride. Triphenylphosphine ditriflate. Triphenyl-phosphine methiodide. 

Other methods for the preparation of cyclohexanecarboxaldehyde include the catalytic hydrogenation of 3-cyclohexene-1-carboxaldehyde, available from the Diels-Alder reaction of butadiene and acrolein, the reduction of cyclohexanecarbonyl chloride by lithium tri-tcrt-butoxy-aluminum hydride,the reduction of iV,A -dimethylcyclohexane-carboxamide with lithium diethoxyaluminum hydride, and the oxidation of the methane-sulfonate of cyclohexylmethanol with dimethyl sulfoxide. The hydrolysis, with simultaneous decarboxylation and rearrangement, of glycidic esters derived from cyclohexanone gives cyclohexanecarboxaldehyde. 

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