General Experimental Procedures. Melting points were
measured with a Buchi melting point B-540 apparatus. The UV
spectra were recorded with a PerkinElmer UV−vis spectrophotometer.
The IR spectra were recorded with a Perkin-Elmer FTS FT-IR
spectrophotometer. The NMR spectra were recorded using 400 MHz
Bruker and 500 MHz Varian UNITY INOVA spectrometers. Chemical
shifts are recorded in parts per million (δ) in CDCl3 and acetone-d6
with TMS as an internal reference. The ESI-TOF-MS data were
measured on a MicroTOF, Bruker Daltonics mass spectrometer.
Quick column chromatography (QCC) and CC were carried out on Si
gel 60 H (Merck, 5−40 μm) and Si gel 100 (Merck, 63−200 μm),
respectively. Precoated plates of Si gel 60 F254 were used for analytical
purposes.