... The volatile 7a and ethylchlorodiazirine were removed under vacuum during the oxidation in DMSO at 0 °C, condensed in pentane at 77 K, and then separated on silica gel using 2:1 pentane/CH 2 Cl 2 to elute the chlorodiazirine, followed by tetrachlorethane to elute 7a. ... 12); RA Moss, L. Maksimovic, DC Merrer; Tetrahedron Lett., 38 (1997), p. 7049. (13); JE Jackson, N. Soundararajan, MS Platz, MTH Liu; J. Am. Chem. Soc., 110 (1988), p. 5595. (14); ...