Asymmetric alkylation of 2-monosubstituted indolin-3-ones

The asymmetric alkylation of 2-monosubstituted indolin-3-ones with optically active phase transfer catalysts (PTCs) has been studied. The prenylation of 2-benzyl indolin-3-one gave 2,2-dialkylated indolin-3-one 9a in 99% yield and 65% enantioselectivity. The alkylation was investigated with various 2-monosubstituted indolin-3-ones 5a-e and alkyl halides. The absolute configuration of 5d was determined by derivatization to the known amino acid.