Crystal structure of 3-(3,4,5-trimethoxyphenyl)-1,2,3,4-tetrahydrocyclopenta[b]indole-2-carboxylic acid

Abstract

In the title compound, C21H21NO5, obtained from a Morita–Baylis–Hillman adduct, the hydrogenated five-membered ring adopts a shallow envelope conformation, with the C atom bearing the carboxylic acid substituent deviating by 0.237 (1) Å from the mean plane of the other four atoms (r.m.s. deviation = 0.007 Å). The dihedral angle between the fused ring system (all atoms; r.m.s. deviation = 0.057 Å) and the pendant trimethoxy benzene ring is 66.65 (3)°. The C atoms of the meta-methoxy groups lie close to the plane of the benzene ring [deviations = 0.052 (1) and −0.083 (1) Å], whereas the C atom of the para-methoxy group is significantly displaced [deviation = −1.289 (1) Å]. In the crystal, carboxylic acid inversion dimers generate R22(8) loops. The dimers are connected by N—H...O hydrogen bonds, forming [011] chains. A C—H...O interaction is also observed.

Keywords

• crystal strycture
• indole skeleton
• Morita–Baylis–Hillman adduct
• hydrogen bonding