10.1021/jo8010057
The study focuses on the synthesis and characterization of ethynylhelicene oligomers with perfluorooctyl side chains, ranging from monomers to pentamers. Utilizing circular dichroism (CD) and vapor pressure osmometry (VPO), the research demonstrates the formation of a helix-dimer, particularly in the case of the pentamer within trifluoromethylbenzene at low temperatures and specific concentrations. A comparison between the perfluorooctyl and decyloxycarbonyl side-chained pentamers reveals that the former exhibits lower solubility in organic solvents, forms a more thermodynamically stable helix-dimer, and shows an inverted mirror image CD spectrum. Additionally, the perfluorooctyl pentamer is found to form a hetero-helix dimer with a decyloxycarbonyl pentamer, indicating a higher stability for the hetero-helix dimer over the homo-helix dimers. This work contributes to the understanding of double-helix structures in synthetic oligomers and their potential applications in supramolecular chemistry.
10.1055/s-0039-1690901
The research focuses on the synthesis and application of chiral P,O-olefin ligands with rotamers for palladium-catalyzed asymmetric allylic substitution reactions. The purpose of this study was to develop a series of phosphine-olefin-type chiral aminophosphines that exist as two rotamers at the C(aryl)-N(amine) bond and to investigate their efficacy as chiral ligands in Pd-catalyzed asymmetric allylic substitution reactions, such as the alkylation of allylic acetates with malonates or indoles. The researchers synthesized a series of chiral aminophosphines, denoted as (S)-6, and confirmed their existence as two rotamers through NMR analysis. The ligands were then tested in Pd-catalyzed reactions, yielding high enantioselectivities, with up to 98% ee achieved. The research concluded that these chiral aminophosphines, particularly (S)-6d and (S)-6a, were effective chiral ligands for the Pd-catalyzed asymmetric allylic alkylation of malonates and indoles, respectively. Key chemicals used in the process included various aminophosphines (S)-6, palladium catalysts, allylic acetates, malonates, indoles, and solvents such as toluene, THF, and (trifluoromethyl)benzene. The research also optimized reaction conditions, including the choice of base and solvent, to achieve the best enantioselectivity.
F,
T,
C,
N
