Journal of the American Chemical Society Supporting Information Page 1 Ni(II) Bis(oxazoline)-Catalyzed Enantioselective Syn Aldol Reactions of N-Propionylthiazolidinethione in the Presence of Silyl Triflates David A. Evans, * C. Wade Downey, and Jed L. Hubbs Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 Supporting Information General Information. Aldol reactions were carried out nitrogen atmosphere with a septum cap and magnetic stirring; no special precautions were taken to exclude water from the reaction vessel. Toluene and CH 2 Cl 2 were purified by passage through a bed of activated alumina. 1 MeOH was distilled from Mg(OMe) 2 . All other reaction solvents were used as received. Benzaldehyde, 2-naphthaldehyde, TESOTf, imidazole, Me(OMe)NH 2 Cl, and AgOTf were used as received from Aldrich Chemical Co. Other aldehydes were distilled from suitable desiccants. NiCl 2 was used as received from Alfa/Aesar Chemical Co. 2,6-Lutidine was distilled from CaH 2 prior to use. TMSOTf was distilled prior to use. Reagents were purified prior to use unless otherwise stated following the guidelines of Perrin and Armarego. 2 Purification of reaction products was carried out by flash chromatography using EM Reagent silica gel 60 (230-400 mesh). Analytical thin layer chromatography was performed on EM Reagent 0.25 mm silica gel 60-F plates. Visualization was accomplished with UV light and ceric ammonium nitrate stain, followed by heating. Optical rotations were measured on a Jasco DIP-0181 digital polarimeter with a sodium lamp and are reported as follows: [α] λ T ° C (c = g/100 mL, solvent). Infrared spectra were recorded on a Perkin Elmer 1600 series FT-IR spectrometer. 1 H-NMR spectra were recorded on a Varian Inova-500 (500 MHz) spectrometer and are reported in ppm using solvent as an internal standard (CDCl 3 at 7.26 ppm). Data are reported as (ap = apparent, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, b = broad; coupling constant(s) in Hz; integration. Proton-decoupled 13 C-NMR spectra were recorded on a Varian Mercury 400 (100 MHz) spectrometer and are reported in ppm using solvent as an internal standard (CDCl 3 at 77.0 ppm). Low- and high- resolution mass spectra were obtained on Jeol AX-505 or SX-102 spectrometers in the Harvard University Mass Spectrometry Laboratory. General Procedure: Nickel-catalyzed direct aldol reaction of N-propionylthiazolidinethione with aldehydes To a 10-mL round-bottom flask in a glove box was added Ni(OTf) 2 (t-BuBox) (0.10 mmol, 0.1 equiv). The flask was fitted with a septum cap and removed to ambient atmosphere. The nickel complex was dissolved in 50 μL CH2Cl2 and 200 μL toluene. After cooling to –78 °C, 2,6-lutidine (3.33 mmol, 3.33 equiv), N- propionylthiazolidinethione (1.0 mmol, 1 equiv), aldehyde (1.2 mmol, 1.2 equiv), and TMSOTf (1.25 mmol, 1.25 equiv) were added sequentially. The yellow reaction mixture was stirred 12-36 h until complete by TLC, then filtered directly through a plug of silica gel (5.0 cm x 5.0 cm) and eluted with Et 2 O. The eluent was concentrated in vacuo and dissolved in THF (10 mL) and treated with 1.0 N HCl (2 mL). After stirring 1 h, the mixture was diluted with Et 2 O (20 mL) and water (20 mL). The layers were separated and the organic layer was extracted sequentially with saturated NaHCO 3 (20 mL) and brine (20 mL). The organic layer was dried over Na 2 SO 4 for 1 h, then filtered through a cotton plug and concentrated in vacuo. A sample was subjected to HPLC analysis to determine enantio- and diastereoselectivity. Flash chromatography (10-20% EtOAc/hexanes) afforded the pure major diastereomer, except where otherwise noted. (1) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.; Timmers, F. J. Organometallics 1996, 15, 1518-1520. (2) Perrin, D. D. and Armarego, W. L. Purification of Laboratory Chemicals; 3 rd ed., Pergamon Press, Oxford. 1988.