Conformational insights into furo- and thieno[2,3-b]indolines derived from coupling constants and molecular modeling.
The extent to which conformational preferences of fused heterocyclic five-membered rings change with the nature of the heteroatom (O and S) was investigated in furo- (1, 2) and thieno[2,3-b]indolines (3, 4) by the combined use of 1H NMR spectroscopy and density functional theory (DFT) calculations. In contrast to the behavior observed for pyrroloindolines, the furo- and thienoindolines exist in solution in only one conformer, with structures in the 2E-2T3 (1,2) and 2T3-E (3,4) North/West region of the pseudorotational wheel, and with pseudorotation phase angles (P) of 315.8, 311.6, 337.2 and 331.6 degrees, respectively.
Morales-Ríos
Martha S
MS
Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México D.F., 07000 Mexico. smorales@mail.cinvestav.mx
Santos-Sánchez
Norma F
NF
Pérez-Rojas
Nadia A
NA
Joseph-Nathan
Pedro
P
D007211:Indoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation
D007211:Indoles; C057812:indoline