Supplementary Material Available; X-ray structure, fractional atomic coordinates, mean square amplitudes of thermal vibration, bond distances, and bond angles of 17 (18 pages). Ordering information is given on any current masthead page.
Scheme III concentrated, and a chromatographic separation under the same conditions as above gave 4b: 75% yield; mp 229-230 °C; mass spectrum, m/e 438; NMR (CDClg) 6.67-6.92 (s, 4 H), 5.7 (d, 1
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