Good yields of three series 39 ee (αS, βR) epoxy ketones were synthesized from theirE-conformers of substituted styryl ketones using chiral quaternary ammonium bromide-PF₆ catalyst. The yields of epoxides were more than 96%. These compounds have been characterized using the microanalytical technique, spectral data and physical constants.

Numerous investigations have been carried out on the catalytic asymmetric epoxidation of α, β-Unsaturated ketones. A number of useful methodologies with various catalyst-reagent combinations have been reported in the literature (Poter and Skidmore, 2000; Nemoto et al., 2002; and Yao and Zhang, 2003). Catalytic asymmetric epoxidation method has occupied a unique place in synthesizing organic substrates, featuring many advantages, including operational simplicity, non-metal catalysts and highly environmental consciousness (O'Donnel, 1993; Poter and Skidmore, 2000; and Shioiri and Arai, 2000). It is reported that since the work of Wynberg with alkylated cinchona alkaloids, we have only a few examples (Hummelen and Wynberg, 1978; and Pluim and Wynberg, 1980). In the 1990s, Lygo and Wainwright (1998), and Lygo et al. (1999) studied the effectiveness of a catalyst incorporating a 9-anthracenyl group in the epoxidation of mainly substituted chalcones with commonly available sodium hypochlorite. Corey and Zhang (1999) reported that the use of the same catalyst with 65% potassium hypochlorite at lower temperature (- 40 °C) leads to improved enantioselectivities. Song et al. (2005) reported that the yield of oxiranes is 77-93% at lower temperatures (-55 °C) using Mn(III) schiff base complex as the catalyst. Many scientists (Ballani and Bosica, 1998; Andic et al., 2003; Ye et al., 2003; Arai et al., 2004; Bako et al., 2004; and Reddy et al., 2005) tested the methods of epoxidation of chalcones, including pyrrole substrates with various catalysts successfully with the yield of 90%. Despite such recent impressive progress, the full potential of this reaction is yet to be realized in the synthesis of keto epoxides (Arai et al., 1998 and 2002; Adam, 2002; and Allingam et al., 2003). Organic chemists and scientists (Du et al., 1986; Jaquinod et al., 1998; and Hashimoto and Maruoka, 2003) reported the mechanistic investigation of the catalyst, and that the yield of expoxides is more than 96% with the desired selectivity. But this type of study with substituted styryl 1-naphthyl, 9H-fluorene-2-yl and 4-biphenyl ketones was not reported in literature in the past. Here, our prime concern is to synthesize the maximum yield of keto epoxides (oxiranes) using a chiral quaternary ammonium bromide-PF₆ (1) catalyst, which effectively catalyzes the epoxidation of α, β-Unsaturated ketones, namely, E-conformers of substituted styryl 4-biphenyl, 9H-fluorene-2-yl and 1-naphthyl ketones with enantioselectivities under mild conditions. However, we have not undertaken a detailed mechanistic investigation of the catalytic reaction.

The uncorrected melting points of the synthesized compounds were found out with an open capillary tube. Using Flash column chromatography on silica gel with ethyl acetate/hexane 1:3 as eluent, the purity of the synthesized epoxides were verified and reported. The enantioselectivity and absolute configuration of oxiranes were determined by comparison of the HPLC retention time using chiral column (Corey and Zhang, 1999) (DAICEL, Chiralal OD). IR spectra were recorded on Perkin-Elmer Fourier transform spectrophotometer in KBr (4000-400 cm^_1) discs. ¹H and ¹³C NMR spectra were recorded in CDCl₃ on INSTRUM DPX-200 model 300 MHz spectrometer operating at 300 MHz frequency for recording H NMR spectra and 75.45 MHz frequency for recording ¹³C NMR spectra, TMS as internal standard. With the help of Perkin-Elmer 240 C analyzer, the elemental analyses of the synthesized oxiranes were performed.

Chemistry Journal, Biphenyl, Fluorenyl, Naphthyl Ketones, Enantioselective Epoxidation, IR Spectroscopy, NMR Spectroscopy, Epoxy Ketones, Chiral Quaternary Ammonium Bromide, Microanalytical Technique, Catalytic Asymmetric Epoxidation, Organic Substrates, HPLC Analysis.