Reaction monitoring: Reactions were monitored by thin layer chromatography (TLC). TLCanalysis was performed on silica gel coated aluminium plates ALUGRAM ® Xtra SIL G/UV 254 purchased from MACHEREY-NAGEL. Products were visualized by UV light at 254 nm and by using staining reagents (based on KMnO 4 , Ce(SO 4 ) 2 and anisaldehyde). constants (J) are given in Hz. Multiplicity is indicated as follows: s (singlet), d (doublet), t (triplet), q (quartet), p (pentet), br (broad) and combinations thereof. In the case where no multiplicity could be identified, the chemical shift range of the signal is given as m (multiplet). C NMR spectra are 1 H-broadband decoupled.