Planar Chiral Analogues of PRODAN Based on a [2.2]Paracyclophane Scaffold: Synthesis and Photophysical Studies

Construction of planar chiral [2,2]paracyclophanes via photoinduced cobalt-catalyzed desymmetric addition

Planar chiral [2,2]paracyclophanes (PCPs) are widely used in materials science and asymmetric syntheses. Therefore, synthetic and material chemists have focused on the efficient and selective construction of planar chiral PCPs for decades. Herein, we present a photoinduced cobalt-catalyzed desymmetric addition of pseudo-para-diformyl and pseudo-gem-diformyl PCP, enabling the synthesis of planar chiral PCP alcohols with both planar and central chiralities. This method delivers 48 examples with yields up to 87%, diastereomeric ratios greater than 19:1, and an enantiomeric excess exceeding 99%. This protocol provides a original and efficient approach for the synthesis of planar chiral PCPs.

Polyaromatic Cyclophanes Design and their Related Optical Properties

In this article, we present several organic synthetic way to synthesize a family of five polyaromatic molecules based on a cyclophane core. Our strategies revolves around palado-catalyzed substitution on a [2.2]paracyclophane (pCp) building block. Direct formation of a cyclophane was also employed for two molecules. The polyaromatic nature of the cyclophane library we synthetized made them good fluorophores candidate, we hence performed full photophysical characterization (Absorption, Emission, TCSPC) in different solvent as well as embed in polystyrene films. We evaluate how the cyclophane moiety influence their photo physical properties compared to their corresponding homologues without pCp core, demonstrating greater stoke shift and intramolecular exciplex behavior. The general behavior among cyclophanes was also compared and show solvent dependent properties as well as consistency of the photophysics between toluene and polystyrene matrix.

Total Synthesis of Homoseongomycin Enantiomers and Evaluation of Their Optical Rotation

A total synthesis of each homoseongomycin enantiomer was accomplished in 17 total steps (longest linear sequence = 12 steps) and 10 chromatographic purifications. Several schemes were attempted to forge the key 5-membered ring, but only a Suzuki coupling-intramolecular Friedel-Crafts acylation sequence proved viable. Challenges encountered during the optical rotation characterization of the natural product left us with two important takeaways. First, highly colored compounds like homoseongomycin that absorb near/at the sodium d-line may require optical rotation measurements at other wavelengths. Second, high dilution of such compounds to obtain measurement at the sodium d-line could result in artificially large and incorrectly assigned specific rotations. To verify the optical rotation, electronic circular dichroism spectra were acquired for both homoseongomycin enantiomers and were transformed into optical rotary dispersions via the Kramers-Kronig transform. We note the wavelength dependency on rotation, and at the sodium d-line 589 nm, we reassign the optical rotation of L-homoseongomycin from (-) to (+).

[2.2]Paracyclophane-based coumarins: effective organo-photocatalysts for light-induced desulfonylation processes

Herein, we demonstrate for the first time that coumarins derived from [2.2]paracyclophane (pCp) can act as effective organo-photocatalysts and promote the reductive cleavage of sulfonamides under light-irradiation. In the presence of these original compounds, photodesulfonylation reactions occur under mild conditions at low catalyst loadings in the presence of Hantzsch ester. Theoretical and experimental investigations are described, which elucidate the reaction mechanism and the nature of the active species involved in the photocatalytic process. This proof-of-concept study paves the way for further application of pCps in the field of photocatalysis.

Synthesis of Two Novel Optically Active #-Shaped Cyclic Tetramers Based on Planar Chiral [2.2]Paracyclophanes

This study reports the synthesis of optically active cyclic tetramers comprising four stacked π-electron systems from two enantiomerically pure [2.2]paracyclophane compounds (bis-(para)-pseudo-ortho- and bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane compounds). Depending on the combination of the absolute configurations of the planar chiral pseudo-ortho- and pseudo-meta-[2.2]paracyclophane units, the cyclic tetramers formed either parallel-#- or weave-#-structures. The optical and chiroptical properties of both structures were investigated experimentally and theoretically. In particular, the weave-#-shaped cyclic tetramer exhibited good chiroptical properties and emitted circularly polarized luminescence (CPL) with a high anisotropy factor (|g_lum | value of the order of 10^-3 ) and a CPL brightness (B_CPL ) higher than 100.