N-protected pyrroles as synthons for variants of core-modified N-confused calixphyrins: Spectroscopic and theoretical characterization

Abstract

A new convergent synthetic methodology has been adopted for syntheses of two hitherto unknown new generation of core-modified N-confused calixphyrins and an all four meso-sp3 centered heterocyclic macrocycle with [Formula: see text],[Formula: see text]-pyrrole connectivities via acid catalyzed Lindsey type condensation of thiophene diol with N-protected pyrrole(s) using BF3.Et2O followed by oxidation with chloranil. All of the macrocycles have been achieved in moderately good yields. Their structures, electronic and optical properties have been elucidated by NMR, UV-Vis-NIR spectroscopic analyses and in-depth theoretical calculations. The type of macrocycles are a mere consequence of the type of N-protected pyrroles used as synthons with the UV-Vis spectra closely resembling the spectra for calixphyrins. Detailed structural analyses using 1H-1H (COSY, ROESY), [Formula: see text]C-1H (HSQC) 2D NMR studies and DFT level theoretical investigations indicated lack of macrocyclic [Formula: see text] conjugation with [Formula: see text],[Formula: see text] and/or [Formula: see text],[Formula: see text] pyrrole connectivities.