HBF4·OEt2 as a versatile reagent for the Hosomi–Sakurai allylation and Prins cyclization: one-pot synthesis of symmetrical 4-fluorotetrahydropyrans

Halocyclobutanol Dehydration En Route to Halocyclobutenes

A new method for the preparation of halocyclobutenes is described. The developed process involves the dehydration of halocyclobutanols by using tetrafluoroboric acid–diethyl ether complex in dichloromethane at room temperature. The process allows for high yields of halocyclobutenes to be achieved by using alcohols that do not trigger the formation of isomeric allylic halides.

Multifaceted Ion Exchange Resin-Supported Hydrogen Fluoride: A Path to Flow Hydrofluorination

A solid anhydrous hydrogen fluoride equivalent was prepared by mixing HF gas with an inexpensive anion exchange resin (A26-HF, HF content 30% wt/wt).

Diastereoselective synthesis of tetrahydropyrans via Prins–Ritter and Prins–arylthiolation cyclization reactions

Highly diastereoselective Prins–Ritter and Prins-arylthiolation cyclization reactions have been developed for the synthesis of two novel classes of tetrahydropyran derivatives.

Preparation of Fluorinated Tetrahydropyrans and Piperidines using a New Nucleophilic Fluorination Reagent DMPU/HF

DMPU/HF (HF content 65 wt %/wt) is an ideal nucleophilic fluorination reagent for the diastereoselective synthesis of substituted 4-fluorotetrahydropyrans and 4-fluoropiperidines via a fluoro-Prins reaction. When compared to classical nucleophilic fluorination reagents like pyridine/HF, DMPU/HF gives both higher yields and better diastereoselectivity.

A Ce(OTf)3/PyBox catalyzed enantioselective Hosomi–Sakurai reaction of aldehydes with allyltrimethylsilane

An approach to the efficient synthesis of enantioselective homoallylic alcohols has been developed by the use of a catalytic amount of a cerium/PyBox complex.

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

A simple, efficient and highly diastereoselective one-pot three-component synthesis of functionalized 2,6-disubstituted-4-tosyloxytetrahydropyrans was performed. The synthesis features an optimized Prins cyclization in which an aromatic homoallylic alcohol, an aromatic/aliphatic aldehyde, and p-toluenesulfonic acid (catalyst and reagent) are reacted in the presence of molecular sieves (MS) 4 Å at reflux in dichloromethane to afford excellent yields (72–96%) within short reaction times (20–90 min). The MS 4 Å-promoted synthesis proved to be versatile enough to provide an array of symmetrical and unsymmetrical tetrahydropyran derivatives in economical manner. Furthermore, cleavage of the 4-tosyl group under mild conditions afforded 4-hydroxytetrahydropyran in excellent yields (95–96%).