Generation of Selenabenzenes Bearing an Electron-Withdrawing Group at me 2-Position.
作者:Tadashi KATAOKA、Yasuhiro OHE、Akira UMEDA、Tatsunori IWAMURA、Mitsuhiro YOSHIMATSU、Hiroshi SHIMIZU
DOI:10.1248/cpb.42.811
日期:——
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 dihydroselenopyrans 2 with 1.5 eq of m-chloroperbenzoic acid provided 2H-selenopyrans 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 trifluoromethanesulfonate 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.
丁二烯与由硒氰酸酯 1 和三乙胺原位生成的硒醛发生 Diels-Alder 反应,制备出了在 2 位上带有一个抽电子基团的 3,6-二氢-2H-硒并吡喃 2。用 1.5 eq 间氯过苯甲酸氧化二氢硒并吡喃 2,可得到 2H-硒并吡喃 9 和 3,6-二氢-2H-硒并吡喃-2-基间氯苯甲酸酯 10。使用多聚磷酸三甲基硅酯可将苯甲酸酯 10 顺利转化为硒黄檀 9。用三氟甲磺酸甲酯将硒基吡喃 9 甲基化,得到 Se-甲基硒基吡喃三氟甲磺酸酯 12。用氢化钠或三乙胺对硒鎓盐 12 进行去质子化反应,生成了硒苯衍生物 13,但它们太不稳定,无法分离出来。因此,我们在 -30°C 温度下通过 1H 和 13C-NMR 光谱确认了 13 的生成。