Asymmetric hydroamination with far fewer chiral species than copper centers achieved by tuning the structure of supramolecular helical catalysts

Abstract

The incorporation of a few chiral monomers (the “sergeants”) in a backbone composed of a majority of achiral monomers (the “soldiers”) is a well-established strategy to control the handedness of...

Probing achiral benzene-1,3,5-tricarboxamide monomers as inducers of homochirality in supramolecular helical catalysts

“…In a related catalytic system, employed in the coppercatalyzed hydroamination of styrene, BTA Achc was found to improve both the extent of the "sergeants-and-soldiers" effect and the enantioselectivity of the reaction, relatively to the additive-free catalyst. [40] For the hydrosilylation reaction reported in the present study, it is possible to play both on the nature of the achiral BTA additive and its amount in order to maintain an optimal selectivity (or close to it) even with a very small quantity of "sergeants" engaged in the catalytic system. The similarities and differences between the assemblies of BTA C8 and BTA Achc, the worst-and the best-performing achiral The main properties of these polymers with very small (fs 0 = 0.5%) and high quantity of "sergeants" (fs 0 > 50%) are compared in the respective tables.…”

“…mixture without achiral additive, [41] since both mixtures show similar FT-IR traces in the 1720-1750 cm -1 region, region in which remaining BTA (S)-Cha dimers can be detected and quantified (Figure S1). [24,[37][38][39][40][41] The amount of BTA (S)-Cha monomers in dimers and stacks is thus estimated to be 0.18±0.13 mM and 0.40±0.13 mM, respectively, that corresponds to 30±20% and 70±20% of BTA (S)-Cha introduced in the solution (the high uncertainty is due to the low intensity of the signals). The simulated spectrum is built by summing the FT-IR spectra of these remaining BTA (S)-Cha dimers (0.18 mM), of BTA P•[Cu] (BTA P 5.8 mM + [Cu(OAc)2•H2O] 1.45 mM), BTA C8 (5.8 mM) and of BTA Met [43] (0.40 mM, in methylcyclohexane, used as blueprint of BTA (S)-Cha monomers in stacks).…”

“…[34,35] In addition to these intriguing effects displayed by small molecules, it seems opportune to use a third component for which the amount can be precisely tuned. Along our interest in developing the catalytic properties of supramolecular BTA coassemblies, [36][37][38][39][40][41] we recently disclosed that the extent of the S&S-effect was increased by two orders of magnitude, reaching homochirality with as low as 0.5% of "sergeants" and close to the optimal enantioselectivity, at the surprizing condition that an achiral BTA monomer was added to the catalytic mixture. [39] Improvement of the catalytic Scheme 1 Molecular structures of the BTA monomers, BTA P as "soldier", BTA (R)-Cha or BTA (S)-Cha as "sergeant" and various achiral BTAs tested as additives, used in this study and schematic representation of the two-component (coassemblies) and three-component (terpolymers) S&S-type assemblies formed without (left) and with (right) achiral additive.…”

“…The influence of the achiral BTA additive is particularly strong for mixtures contain low fractions of "sergeants" (i.e. BTA (R)-Cha or BTA (S)-Cha), quantified as fs 0 enantioselectivity at very low fraction of "sergeants" was observed in both the copper-catalyzed hydrosilylation [39] and hydroamination [40] reactions. The counterintuitive property of this BTA additive, derived from the ester of 1-aminocyclohexane carboxylic acid (BTA Achc, Scheme 1), to induce homochirality in supramolecular helical catalysts was attributed to its ability to stabilize the coassemblies and to suppress helix reversals, i.e.…”

Micelle and Nanotape Formation of Benzene Tricarboxamide Analogues with Selective Cancer Cell Cytotoxicity

“…Molecules based on benzene-1,3,5-tricarboxamide (BTA) have been shown to have many interesting properties, ,,− since they are model supramolecular polymers with a rigid π-stacking benzene motif surrounded by three hydrogen-bonding amide groups forming trifunctionalized self-assembling molecules. BTA derivatives have potential applications such as organo- and metallocatalysis − and the development of biomaterials and stimuli-responsive materials . In another interesting recent example, BTA has been used as a scaffold to prepare trifunctional di- and tripeptide derivatives containing diphenylalanine as a common motif that favors β-sheet formation .…”