The title compound, C13H13NO3, was synthesized by acetyl­ation of ethyl 1H-indole-3-carboxyl­ate. The aromatic ring system of the mol­ecule is essentially planar, but the saturated ethyl group is also located within this plane and the overall r.m.s. deviation from planarity is only 0.034 Å. Pairs of C—H⋯O inter­actions connect mol­ecules into chains along the diagonal of the unit cell. Mol­ecules also form weakly connected dimers via π⋯π stacking inter­actions of the indole rings with centroid–centroid separations of 3.571 (1) Å. C—H⋯π inter­actions between methyl­ene and methyl groups and the indole and benzene ring complete the directional inter­molecular inter­actions found in the crystal structure.

An unusual reduction of the aryl-substituted 3-hydroxyacrylic acid ester 1 by BH 3 results in the propenoic acid ethyl ester 3. We were able to proVe the presence of an intermediate 2 containing a cyclic O-BH 2 r OdC< moiety in 2 by using 1 H-11 B and 1 H-13 C{ 11 B} NMR correlation experiments.