A mild, efficient and alpha-selective glycosidation by using potassium dodecatungstocobaltate trihydrate as catalyst

Flash Electrochemical Approach to Carbocations

A novel flow electrochemical reactor that accomplishes electrolysis within a few seconds in a single passage was developed. By using the flow reactor system, the flash electrochemical generation of short-lived carbocations, including oxocarbenium ions, N -acyliminium ions, glycosyl cations, and Ferrier cations was achieved within a few seconds, enabling the subsequent reaction with nucleophiles before their decomposition. Moreover, continuous operation based on the present system enabled the rapid synthesis of pharmaceutical precursors on demand.

Chemical O-Glycosylations: An Overview

The development of glycobiology relies on the sources of particular oligosaccharides in their purest forms. As the isolation of the oligosaccharide structures from natural sources is not a reliable option for providing samples with homogeneity, chemical means become pertinent. The growing demand for diverse oligosaccharide structures has prompted the advancement of chemical strategies to stitch sugar molecules with precise stereo- and regioselectivity through the formation of glycosidic bonds. This Review will focus on the key developments towards chemical O-glycosylations in the current century. Synthesis of novel glycosyl donors and acceptors and their unique activation for successful glycosylation are discussed. This Review concludes with a summary of recent developments and comments on future prospects.

Heterogenization of heteropoly compounds: a review of their structure and synthesis

The heterogenization of different types of heteropoly compoundsviasix popular methods from those published over the past recent 15 years is reviewed.

NaHSO(4) supported on silica gel: an alternative catalyst for Ferrier rearrangement of glycals

NaHSO(4) supported on silica gel catalyses the Ferrier rearrangement reaction of 3,4,6-tri-O-acetyl-D-glucal with alcohols and thiols to give the corresponding 2,3-unsaturated glycosides in high anomeric selectivity and good to excellent yield in short reaction time.

H3PW12O40 — A selective, environmentally benign, and reusable catalyst for the preparation of methoxymethyl and ethoxymethyl ethers and their deprotections under mild conditions

Different types of primary and secondary alcohols were efficiently transformed to their corresponding methoxymethyl (MOM) and ethoxymethyl (EOM) ethers in the presence of catalytic amounts of H3PW12O40 at room temperature under solvent-free conditions. Selective protection of primary and secondary alcohols in the presence of phenols and tertiary alcohols was achieved by this method. Deprotection of these ethers to their parent alcohols was also performed using this catalyst in ethanol under reflux conditions. We have also found that primary and secondary MOM- and EOM-ethers are selectively deprotected in the presence of phenolic and tertiary ones, methyl and benzyl ethers, esters, and trimethylsilyl ethers by this catalyst. The notable advantages of this protocol are high yields, short reaction times, easy work-up, non-toxicity, easy availability and handling, eco-friendly, and reusability of the catalyst.Key words: methoxymethylation, ethoxymethylation, protection, deprotection, heteropoly acid.

Cobaltpolyoxometalate-catalyzed cyclization of glucal with aryl amines: Synthesis of 2,4-disubstituted tetrahydroquinolines

Treatment of 3,4,6-tri-O-acetyl-d-glucal (1) with various aryl amines in the presence of dodecatungstocobaltate under mild and neutral conditions gave sugar derived tetrahydroquinoline derivates.

A practical and green approach towards synthesis of dihydropyrimidinones: Using heteropoly acids as efficient catalysts

A simple and green chemistry procedure for the synthesis of dihydropyrimidinones using heteropoly acid mediated cyclocondensation reaction is described. This method provides an efficient and much improved modification of the original Biginelli reaction reported in 1893, in terms of high yields, and short reaction times. It has the ability to allow a wide variety of substitutions in all three components.

Heteropoly acids as solid green Brønsted acids for a one-pot synthesis of β-acetamido ketones by Dakin–West reaction

An efficient improved procedure for the synthesis of beta-acetamido ketones has been developed by a heteropoly acid (HPA) catalyzed three-component coupling protocol. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times, and mild conditions.