12 Feb 09:11
by Wenping Luo,
Yewen Fang,
Li Zhang,
Tianhang Xu,
Yongjun Liu,
Yan Li,
Xiaoping Jin,
Jiakan Bao,
Xiaodong Wu,
Zongyong Zhang
A new bifunctional C1 synthon: With bromomethyl silicate as a CH2 source, visible‐light‐induced cyclopropanation has been demonstrated to be amenable to the alkenes including Michael acceptors, styrene derivatives, and unactivated 1,1‐dialkyl ethylenes. In addition to the broad substrate scope, this radical‐polar crossover process is also characterized by its redox‐neutral process, mild conditions, and good functional‐group compatibility.
A general protocol for visible‐light‐induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α‐aryl or methyl‐substituted Michael acceptors and styrene derivatives, the unactivated 1,1‐dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3‐bis(1‐arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late‐stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.
04 Oct 06:24
by Rui Zhang, Lei Wang, Zheqi Shen, Min Li, Xuhong Guo, Yuan Yao
Abstract
Spherical polymer brushes, poly(acrylic acid) (PAA)-grafted polystyrene nanoparticle (PAA@PS), are employed as the macro-crosslinker to prepare PAA hydrogels. Benefitting from the innumerable hydrogen bonds between highly entangled PAA chains both in bulk and on the polymer brush, the PAA/PAA@PS hydrogels combine desirable stretchability, toughness, and notch-insensitivity. The uniaxial tensile tests show a very high fracture elongation up to 9.1 × 103% while the fracture toughness reaches 3.0 MJ m−3 and the maximum swelling ratio of the hydrogel can be 2.0 × 103 as well. After being loaded with silver nanoparticles, the PAA/PAA@PS hydrogels are employed as a recyclable catalyst successfully.
Spherical polyelectrolyte brushes are adopted as the macro-crosslinker to prepare poly(acrylic acid) hydrogels through innumerable hydrogen bonds. The obtained ultrastretchable hydrogels combine desirable stretchability, toughness, and notch-insensitivity. After being loaded with silver nanoparticles, the hydrogel can be employed as a recyclable catalyst.
12 Sep 04:00
by Yu Liu, Xin Zhang, Yun Lei Tan, Gira Bhabha, Damian C. Ekiert, Yakov Kipnis, Sinisa Bjelic, David Baker and Jeffery W. Kelly
Journal of the American Chemical Society
DOI: 10.1021/ja5056356
