Generation of selenabenzenes bearing an electron-withdrawing group at the 2-position

Article abstract of DOI:10.1248/cpb.42.811

3,6-Dihydro-2H-selenopyrans 2 with an electron-withdrawing group at the 2-position were prepared by the Diels-Alder reaction of butadienes with selenoaldehydes generated in situ from selenocyanates 1 and triethylamine. Oxidation of the dihydroselenopyraus 2 with 1.5 eq of m-chloroperbenzoic acid provided 2H-selenopyraus 9 and 3,6-dihydro-2H-selenopyran-2-yl m-chlorobenzoates 10. The benzoates 10 were smoothly converted into the selenopyrans 9 using polyphosphoric acid trimethylsilyl ester. The selenopyrans 9 were methylated with methyl trifluoromethanesuflonate to give Se-methyl selenopyranium trifluoromethanesulfonates 12. Deprotonation of the selenonium salts 12 with sodium hydride or triethylamine generated the selenabenzene derivatives 13, but they were too unstable to be isolated. Therefore, we confirmed the generation of 13 by ¹H- and ¹³C-NMR spectroscopy at -30°C.

Full text of DOI:10.1248/cpb.42.811

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