Studies toward a library of tetrahydrofurans: click and MCR products of mono- and bis-tetrahydrofurans.

Overview

Mono- and bis-tetrahydrofuran-based chemical libraries with diverse structural features have been prepared using the Sharpless azide-alkyne Click reaction and multi-component reactions (MCRs) such as Ugi and Biginelli reactions. Mono- and bis-tetrahydrofuran methyl azides, amines and ureas were key intermediates in these processes, and they were synthesized from the corresponding tetrahydrofuran methyl alcohols by mesylation followed by substitution with azide, reduction of the azide to the amine, and urea formation, as needed. Most mono- and tetrahydrofuran methyl alcohols were obtained by a Sharpless asymmetric dihydroxylation reaction. Alternatively, several mono-tetrahydrofurans were prepared by a cobalt(II) complex-catalyzed oxidative cyclization of bis-homoallylic alcohols, which were obtained by copper(I) iodide-catalyzed epoxide opening of 5,6-epoxyhex-1-ene with various alkyl and aryl Grignard reagents. These compounds are examples of an entirely new class of molecules in hitherto unknown chemical space, though their functions are yet to be determined presumably through random screening.