H and 13 C NMR Spectra 1) 4,4,5,5-Tetramethyl-2-phenyl-1,3-dioxolane (2)2) 2-(3-Chloropropyl)-4,4,5,5-tetramethyl-1,3-dioxolane ( 17)3) 2-(2-Bromoethyl)-4,4,5,5-tetramethyl-1,3-dioxolane (18) 4) 4-Iodo-5-methyl-5- ((4,4,5,5-
Experimental ProceduresGeneral. Flash column chromatography 1 was carried out using Merck SiO 2 60 (230-400 mesh), and thin layer chromatography (TLC) was carried out using commercially available Merck F 254 precoated sheets. 1 H and 13 C NMR spectra were recorded on a Bruker AVANCE 300 or on an AM-400 spectrometer. Chemical shifts are given in ppm and were referenced using residual signals of the solvent as internal standard ( 1 H: CHCl 3 , 7.26; 13 C: CDCl 3 , 77.16). IR spectra were recorded on a Bruker IFS-88 spectrometer. Mass spectra were recorded on a Finnigan MAT-90 mass spectrometer.General procedure (GP). Pinacol (6 eq.) is placed in a flask, evacuated and flushed with Ar (4×). TFA (5 mL / 6 mmol pinacol) is added and the solution is stirred until pinacol is completely dissolved. The solution is cooled (0 °C) and the glycol acetal (1 eq.) is added. After stirring at 0 °C for 30 min, the mixture is carefully dissolved in an excess of a satd. aq.NaHCO 3 soln and extracted with EtOAc (3×50 mL). The combined organic layers are washed with brine (3×50 mL), dried (Na 2 SO 4 ) and concentrated. The crude product is purified by flash column chromatography (silica gel). 4,4,5,5-Tetramethyl-2-phenyl-1,3-dioxolane (2). 2 2-Phenyl-1,3-dioxolane (1) and pinacol were reacted according to the GP. Chromatography (hexanes/EtOAc/Et 3 N, 250:10:1) afforded 2 (286 mg, 68%) as a colorless oil. R f = 0.75 (hexanes/EtOAc, 3:1). IR (ATR): ν ~ (cm −1 )