Tandem silica gel-catalysed rearrangements and subsequent Baeyer–Villiger reactions of artemisinin derivatives

Abstract
Novel silica gel-catalysed reactions of dihydroartemisinin 1b to deoxyartemisinin 11 and 11β-hydroxy-11-epidihydroartemisinin 8 to compound 9 under mild conditions are described. The structures of the products were determined by mass spectrometry and 1D- and 2D-NMR spectroscopy. A mechanism for their formation is proposed.