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• 4021-08-3 4-methylpicolinic acid 

Relevant academic research and scientific papers

A deep insight into polybenzoxazole formation in the heterocycle-containing polybenzoxazine: An enlightening thought for smarter precursor design

When artificially introducing an ortho-amide group into benzoxazine monomer, the conversion of polybenzoxazine (PBZ) into polybenzoxazole (PBO) could happen at higher temperature. However, the mechanism investigation for this reaction is far from enough,

Atroposelective Synthesis of Axially Chiral Styrenes via an Asymmetric C–H Functionalization Strategy

Axially chiral styrenes, which exhibit a chiral axis between a substituted alkene and an aromatic ring, have been largely overlooked. The hurdle is the lower barriers to rotation compared with that of their biaryl counterparts, rendering their asymmetric synthesis more difficult. We report herein the highly atroposelective synthesis via a C?H functionalization strategy of axially chiral styrenes with an open-chained alkene. Various axially chiral styrenes were produced by Pd(II)-catalyzed C?H alkenylation and alkynylation in good yields (up to 99%) and enantioselectivities (up to 99% ee) by using L-pyroglutamic acid as an inexpensive chiral ligand. The potent application of the styrene atropisomers is demonstrated by a Co(III)-catalyzed enantioselective C?H amidation of ferrocene with axially chiral styrene-type acid as chiral ligand. Experimental and computational studies were conducted to elucidate the reaction mechanism. The chiral induction model of the enantioselectivity-determining C?H bond activation step was also provided based on DFT calculations. Atropisomerism, which stems from the hindered rotation around a chiral axis, is widely present in natural products, pharmaceuticals, and chiral catalysts or ligands. In contrast to the well-investigated biaryl atropisomers, the asymmetric synthesis of axially chiral styrenes bearing a chiral axis between an alkene and an aromatic ring remains a significant challenge. Here, we report a highly atroposelective synthesis of styrene atropisomers with open-chained alkene by asymmetric C?H functionalization by using available L-pyroglutamic acid as a chiral ligand. This strategy enables rapid access to a broad range of enantio-enriched axially chiral styrenes under mild conditions in an atom- and step-economical manner. The resulting axially chiral styrenes are important precursors for further elaborations, including the transformation into axially chiral styrene-type acids, which were demonstrated to be efficient chiral ligands in Co(III)-catalyzed enantioselective C?H amidation reactions. An asymmetric C–H functionalization strategy with L-pGlu-OH as chiral ligand has been developed for the atroposelective synthesis of styrene atropisomers with open-chained alkene. The strategy allows quick access to a wide range of enantio-enriched axially chiral styrenes in high yields and enantioselectivities. The axially chiral styrene-derived chiral acids have been demonstrated to be an efficient type of chiral ligands in Co(III)-catalyzed enantioselective C?H amidation reactions.

Rh-Catalyzed Annulative Insertion of Terminal Olefin onto Pyridines via a C-H Activation Strategy Using Ethenesulfonyl Fluoride as Ethylene Provider

A Rh(III)-catalyzed annulative insertion of ethylene onto picolinamides was achieved, providing a portal to a class of unique pyridine-containing molecules bearing a terminal olefin moiety for diversification. Application of this method for modification of Sorafenib was also accomplished.