We have discovered a new flex-activated mechanophore that releases an N-heterocyclic carbene (NHC) under mechanical load. The mechanophore design is based upon NHC-carbodiimide (NHC-CDI) adducts and demonstrates an important first step toward flex-activated designs capable of further downstream reactivities. Since the flex-activation is non-destructive to the main polymer chains, the material can be subjected to multiple compression cycles to achieve iterative increases in the activation percentage of mechanophores. Two different NHC structures were demonstrated, signifying the potential modularity of the mechanophore design.
An efficient method to synthesize β-ketonitriles from silyl enol ethers by an umploung hypervalent iodine(III)-CN species generated in situ from PhIO/BF3·Et2O/TMSCN has been developed for the first time. This method can be applied to structurally diverse aromatic and aliphatic substrates and further extended to preparation of bioactive compounds like 5-aminopyrazole and 5-aminoisoxazole.
A well-controlled
piezoelectrically mediated reversible addition–fragmentation
chain-transfer polymerization (piezo-RAFT) was carried out under ultrasonic
agitation with piezoelectric ZnO nanoparticles as the mechanochemical
transducer. The resulting polymer had high end-group fidelity, low
dispersity, and capacity for chain extension. This piezoelectrically
mediated polymerization involves the generation of the alkyl radical
through an electron transfer process from the piezoelectric nanoparticle
to alkyl bromide, which was also verified by 1H NMR, liquid
chromatography–mass spectrometry (LC-MS), electron spin resonance
(ESR), and density functional theory (DFT) calculation. This chemistry
was further adopted in curing composite resins to circumvent the light
penetration limit of ultraviolet (UV) curing. This work opens a new
avenue for piezoelectrically mediated chemistry and shows good potential
in curing applications.
A convenient and efficient method for the synthesis of various structurally functionalized sulfinates shows good substrate generality of alcohols and sodium sulfinates.
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