Recyclable DMAP-Functionalized polymeric nanoreactors for highly efficient acylation of alcohols in aqueous systems

Chitosan nanoreactor modified with PNIPAAm as efficient catalyst for preparation of chiral boron compounds in aqueous phase

This work constructed chitosan-based core-shell catalytic nanoreactor (CS/NI/SA@Cu(II)) by free radical polymerization of biomass chitosan and temperature sensitive materials. The CS/NI/SA@Cu(II) were characterized by FT-IR, TG, XPS, SEM, TEM, and EDS to prove the formation of the nanoreactor, and the Cu content was obtained by ICP analysis. The TEM indicated that CS/NI/SA-2 presented a hollow core-shell structure with a size of about 100 nm, and the contact angle of CS/NI/SA-2 was 67°. The core-shell nanoreactors were successfully applied to the 1,4-chiral borylation reaction of α,β-unsaturated compounds, and α,β,γ,δ-unsaturated compounds, as well as the 1,6-chiral borylation reaction of methylene benzoquinone compounds in the aqueous phase. All template substrates can obtain up to 90 % yields with 90 % ee values in core-shell nanoreactors and chiral ligand in 12 h. The possible mechanism of catalytic reaction was revealed by calculation and deuteration experiment. Besides, the CS/NI/SA@Cu(II) could be easily recycled and effectively reused. Besides, the CS/NI/SA@Cu(II) could be easily recycled and effectively reused for 6 times. Remarkably, this approach provides the first report of biomass chitosan for an efficient strategy to gain chiral organic boron compounds in high yields and enantioselectivities.

TEMPO-Functionalized Nanoreactors from Bottlebrush Copolymers for the Selective Oxidation of Alcohols in Water

Polymeric nanoreactors in water fabricated by the self-assembly of amphiphilic copolymers have attracted much attention due to their good catalytic performance without using organic solvents. However, the disassembly and instability of relevant nanostructures often compromise their potential applicability. Herein, the preparation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-containing nanoreactors by the self-assembly of amphiphilic bottlebrush copolymers has been demonstrated. First, a macromonomer having a norbornenyl polymerizable group was prepared by RAFT polymerization of hydrophobic and hydrophilic monomers. The macromonomer was further subjected to ring-opening metathesis polymerization to produce an amphiphilic bottlebrush copolymer. Further, TEMPO, as a catalyst, was introduced into the hydrophobic block through the activated ester strategy. Finally, TEMPO-functionalized polymeric nanoreactors were successfully obtained by self-assembly in water. The nanoreactors exhibited excellent catalytic activities in selective oxidation of alcohols in water. More importantly, the reaction kinetics showed that the turnover frequency is greatly increased compared to that of the similar nanoreactor prepared from liner copolymers under the same conditions. The outstanding catalytic activities of the nanoreactors from bottlebrush copolymers could be attributed to the more stable micellar structure using the substrate concentration effect. This work presents a new strategy to fabricate stable nanoreactors, paving the way for highly efficient organic reactions in aqueous solutions.