Scheme 1. Direct synthesis of a,b-epoxy ketones. Table 2. Synthesis of a,b-epoxy ketone from various aldehydes with substituted styrenes. [a] 3 a, 96 (91) % 3 b, 95 (90) % 3 c, 95 (90) % 3 d, 94 (91) % 3 e, 96 (91) % 3 f, 98 (94) % 3 g, 93 (88) % 3 h, 96 (91) % 3 i, 89 (82) % 3 j, 95 (91) % 3 k, 96 (90) % 3 l, 97 (92) % 3 m, 94 (90) % 3 n, 96 (91) % 3 o, 93 (88) %[a] Conditions: 1 (0.5 mmol), 2 (1.0 mmol), TBHP (1.0 mmol), METS-10 (40 mg), MeCN (2.0 mL), 90 8C, 10 h. [b] Obtained by GC analysis; isolated yields given in parentheses.Figure 2. EPR spectra of a series of reaction mixtures at 70 8C: a) PBN and CH 3 CN; b) METS-10 catalyst, PBN, and CH 3 CN; c) PBN, CH 3 CN, and TBHP; and d) METS-10 catalyst, PBN, CH 3 CN, and TBHP.