Heterogeneous simplified Maruoka phase-transfer catalyst tethered on poly(styrene-co-acrylamide) microsphere: Structure-activity relationship in enantioselective α-alkylation

Machine learning glass transition temperature of styrenic random copolymers

For styrenic random copolymers, the glass transition temperature, Tg, is an important thermophysical parameter, which is sometimes difficult to measure and determine by experiments. Approaches based on data-driven modeling provide alternative methods to predict Tg in a fast and robust way. The Gaussian process regression (GPR) model is investigated to present the statistical relationship between important quantum chemical descriptors and glass transition temperature for styrenic random copolymers. 48 samples with Tg that have been measured experimentally are explored, which range from 246 K to 426 K. The modeling approach demonstrates high accuracy and stability, and provides a novel and promising tool for efficient and low-cost estimations of copolymer Tg values.

Synthesis of Both Enantiomers of Chiral Phenylalanine Derivatives Catalyzed by Cinchona Alkaloid Quaternary Ammonium Salts as Asymmetric Phase Transfer Catalysts

A practical synthesis of both enantiomers of unnatural phenylalanine derivatives by using two pseudoenantiomeric phase transfer catalysts is described. Through asymmetric α-alkylation of glycine Schiff base with substituted benzyl bromides and 1-(bromomethyl)naphthalene under the catalysis of O-allyl-N-(9-anthracenmethyl) cinchoninium bromide (1f) and O-allyl-N-(9-anthracenylmethyl)cinchonidium bromide (1i), respectively, a series of both (R)- and (S)-enantiomers of unnatural α-amino acid derivatives were obtained in excellent yields and enantioselectivity. The synthetic method is simple and scalable, and the stereochemistry of the products is fully predictable and controlled: the cinchonine-type phase transfer catalyst 1f resulted in (R)-α-amino acid derivatives, and the cinchonidine-type phase transfer catalyst 1i afforded (S)-α-amino acid derivatives.

Quaternary ammonium functionalized Fe3O4 & P(GMA-AA-DVB) magnetic Janus particles as highly efficient catalysts for phase transfer reactions

Magnetic Janus quaternary ammonium phase transfer catalysts possess excellent catalytic efficiency and are easy to recycle.