Selective oxidation of cyclopentene with H2O2 by using H3PW12O40 and TBAB as a phase transfer catalyst

Hydrothermal Modification of TS-1 Zeolites with Organic Amines and Salts to Construct Highly Selective Catalysts for Cyclopentene Epoxidation

Developing efficient heterogeneous catalysts for cyclic olefins epoxidation is highly attractive for meeting the growing need for various cyclic epoxides. Herein, hierarchical TS-1 zeolite with relatively abundant mesopores and less amount of surface hydroxyl groups was obtained by hydrothermal modification of an as-synthesized TS-1 zeolite with a mixed solution of ammonia, tetrapropylammonium bromide (TPABr) and KCl. The post-modified TS-1 zeolite exhibited much higher catalytic activity (52% conversion) and epoxide selectivity (98%) for the epoxidation of cyclopentene than the conventional TS-1 zeolites. The excellent catalytic activity of the hierarchical TS-1 could be mainly assigned to the enhancement of the mass transport ability and the accessibility of the active Ti species, while the improvement of epoxidation selectivity may be mainly related to the introduction of a certain amount of K+ that can effectively modulate the coordination environment of Ti species as well as the polarity of the zeolite. This work demonstrated that a highly active and selective catalyst for the H2O2-mediated cyclopentene epoxidation could be obtained by concurrently generating mesopore and extinguishing the unfavorable defective hydroxyl groups through the simple hydrothermal treatment of the conventional TS-1 zeolite with a mixed base/salt solution.

Set of Cytochrome P450s Cooperatively Catalyzes the Synthesis of a Highly Oxidized and Rearranged Diterpene-Class Sordarinane Architecture

Cytochrome P450s are one of the most versatile oxidases that catalyze significant and unique chemical transformations for the construction of complex structural frameworks during natural product biosynthesis. Here, we discovered a set of P450s, including SdnB, SdnH, SdnF, and SdnE, that cooperatively catalyzes the reshaping of the inert cycloaraneosene framework to form a highly oxidized and rearranged sordarinane architecture. Among them, SdnB is confirmed to be the first P450 (or oxidase) that cleaves the C-C bond of the epoxy residue to yield formyl groups in pairs. SdnF selectively oxidizes one generated formyl group to a carboxyl group and accelerates the final Diels-Alder cyclization to furnish the sordarinane architecture. Our work greatly enriches the enzyme functions of the P450 superfamily, supplies the missing skills of the P450 synthetic toolbox, and supports them as biocatalysts in further applications toward the synthesis of new chemical entities.