An efficient sodium hydrogen sulfate catalyzed alkylation of indoles or amines with tertiary enamides has been accomplished in water, affording the pharmacologically and biologically active 2-oxo-1-pyrrolidine derivatives in moderate to excellent yields. The key to our success is the use of NaHSO₄ as a low loading, inexpensive, green and recyclable catalyst and the reactions could be scaled up to gram level.