Catalytic alkylation reactions of weakly acidic carbonyl and related pronucleophiles such as amides, esters, and sulfonamides with substituted alkenes have been reported. In the presence of a strong Brønsted base catalyst system, potassium hexamethyldisilazide and 18-crown-6 ether, the desired reactions proceeded in high yields at ambient temperature with a wide substrate scope. These are atom-economical catalytic alkylation reactions of carbonyl and related compounds.