All solvents and commercially available chemicals
(Sigma-Aldrich, Biosynth Carbosynth, VWR) were used as received unless
otherwise stated. Reactions requiring anhydrous conditions were conducted
with dry solvents under inert atmosphere (nitrogen). Dry dichloromethane
(DCM) was obtained from distillation of DCM (Sigma-Aldrich) over phosphorus
pentoxide (Sigma-Aldrich, >98%) under N2. 2,2′-Azobis(2-methylpropionitrile)
(AIBN, Sigma-Aldrich, >98%) and 3,6-dimethyl-1,4-dioxane-2,5-dione
(Sigma-Aldrich, 99%) were respectively recrystallized from methanol
and ethyl acetate and dried under vacuum. 1,8-Diazabicyclo[5.4.0]undec-7-ene
(DBU, Sigma-Aldrich) was distilled before use. NMR spectra were recorded
on a Varian 500 MHz spectrometer, and δ values are given in
parts per million (ppm).
(Sigma-Aldrich, Biosynth Carbosynth, VWR) were used as received unless
otherwise stated. Reactions requiring anhydrous conditions were conducted
with dry solvents under inert atmosphere (nitrogen). Dry dichloromethane
(DCM) was obtained from distillation of DCM (Sigma-Aldrich) over phosphorus
pentoxide (Sigma-Aldrich, >98%) under N2. 2,2′-Azobis(2-methylpropionitrile)
(AIBN, Sigma-Aldrich, >98%) and 3,6-dimethyl-1,4-dioxane-2,5-dione
(Sigma-Aldrich, 99%) were respectively recrystallized from methanol
and ethyl acetate and dried under vacuum. 1,8-Diazabicyclo[5.4.0]undec-7-ene
(DBU, Sigma-Aldrich) was distilled before use. NMR spectra were recorded
on a Varian 500 MHz spectrometer, and δ values are given in
parts per million (ppm).