A, 3-enals

E)-a Enals.1 The ylide derived from 1 (K2C03) reacts with aldehydes in THF/ether to give (E)-a,0-enals in 80-95% yield. 

Silylformylation of alkynes.1 0-Silyl-a,0-enals can be prepared by reaction of dimethylphenylsilane and carbon monoxide with alkynes catalyzed by Rh4(CO)12. Yields are improved if triethylamine is also present. Regioselectivity in the reaction with internal alkynes is controlled by steric factors. 

Reduction of enediones.1 1,4-Enediones and 4-oxo-2-alkenals are reduced to saturated 1,4-dicarbonyl compounds in nearly quantitative yield by a large excess of Nal-HCl (1 1) in acetone. The method is ineffective with butenedioic acids and a,/ -enones and a,0-enals. 

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