Flyby reaction trajectories: Chemical dynamics under extrinsic force.
Science (New York, N.Y.)
2021; 373 (6551): 208-212
Dynamic effects are an important determinant of chemical reactivity and selectivity, but the deliberate manipulation of atomic motions during a chemical transformation is not straightforward. Here, we demonstrate that extrinsic force exerted upon cyclobutanes by stretching pendant polymer chains influences product selectivity through force-imparted nonstatistical dynamic effects on the stepwise ring-opening reaction. The high product stereoselectivity is quantified by carbon-13 labeling and shown to depend on external force, reactant stereochemistry, and intermediate stability. Computational modeling and simulations show that, besides altering energy barriers, the mechanical force activates reactive intramolecular motions nonstatistically, setting up "flyby trajectories" that advance directly to product without isomerization excursions. A mechanistic model incorporating nonstatistical dynamic effects accounts for isomer-dependent mechanochemical stereoselectivity.
View details for DOI 10.1126/science.abi7609
View details for PubMedID 34244412
Architecture-Controlled Ring-Opening Polymerization for Dynamic Covalent Poly(disulfide)s
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2019; 141 (43): 17075–80
A strategy is reported for controlling the architecture of poly(disulfide)s by ring-opening polymerization. Aryl thiol initiators shift the ring-chain equilibrium to yield cyclic polymers, while alkyl thiols favor linear ones. Control over polymerization enables synthesis of large polymers (630 kDa) and catalytic depolymerization to recycle monomers. This work provides a new avenue to create dynamic covalent polymers with controlled geometry and length, allowing better characterization of structure-property relationships to expand their materials potentials.
View details for DOI 10.1021/jacs.9b08957
View details for Web of Science ID 000493866300008
View details for PubMedID 31603692