General Details. Dimethylformamide and tetrahydrofuran were dried by passage through cylinders of activated alumina. Chloroform was dried over 4 Å molecular sieves and Na2SO4 under Ar overnight. Flash chromatography was conducted using 60-230 mesh silica gel. H NMR spectra were acquired on a 500 MHz spectrometer with chloroform (7.27 ppm) as internal reference. Signals are reported as follows: s (singlet), d (doublet), t (triplet), q (quartet), quint (quintet), dd (doublet of doublets), br s (broad singlet), m (multiplet). C NMR spectra were acquired on a spectrometer operating at 125