作者:Masanori Wada、Hisashi Mishima、Tetsuya Watanabe、Satoko Natsume、Hideki Konishi、Katsuhiko Kirishima、Shuichi Hayase、Tatsuo Erabi
DOI:10.1246/bcsj.68.243
日期:1995.1
A series of triarylmethanols bearing o-methoxyl groups (1a: [2,6-(MeO)2C6H3]3COH, 1b: (2-MeOC6H4)[2,6-(MeO)2C6H3]2COH, 1c: Ph[2,6-(MeO)2C6H3]2COH, 1d: [2,5-(MeO)2C6H3]3COH, 1e: Ph2[2,6-(MeO)2C6H3]COH) were prepared. Corresponding carbenium salts, [Ar3C]X 2a—c, were isolated by short-period treatments of Ar3COH 1a—c with a slight excess of acid in some bulky alcohols, such as 2-propanol or 2-methyl-1-propanol. The high basicity of 1a—c was explained by through-space interactions of a pair of 2p electrons of an o-methoxyl oxygen with an empty 2p orbital of the resulting carbenium carbon. In ethanol, 1-butanol or 3-methyl-1-butanol, 1c, as well as 2c, was reduced under very mild conditions to triarylmethane, Ar3C–H 3c, and in other bulkier alcohols it was reduced under more forcing conditions. The formations of aldehyde or ketone, the by-product, were confirmed in some cases. Compounds 1a,b,d,e, as well as 2a,b, reacted in analogous manners under more forcing conditions. The reaction rates in several alcohols increased in the order 2a < 2b < 2c, and the reaction rates of alcohol for 2c decreased in the order ethanol > 3-methyl-1-butanol > 1-butanol > 2-propanol > methanol > 2-butanol > 2-methyl-1-propanol. Compounds 2b,c were also reduced in tetrahydrofuran, and formed xanthene derivatives in dimethyl sulfoxide or in water.
一系列带有邻甲氧基的三芳基甲醇(1a: [2,6-(MeO)2C6H3]3COH, 1b: (2-MeOC6H4)[2,6-(MeO)2C6H3]2COH, 1c: Ph[2,6-(MeO)2C6H3]2COH, 1d:[2,5-(MeO)2C6H3]3COH,1e:Ph2[2,6-(MeO)2C6H3]COH)。Ar3COH 1a-c 在一些笨重的醇类(如 2-丙醇或 2-甲基-1-丙醇)中与少量过量的酸进行短时间处理后,分离出相应的硒盐 [Ar3C]X 2a-c。1a-c 的高碱性是由于邻甲氧基的一对 2p 电子与生成的硒碳的空 2p 轨道发生了通空作用。在乙醇、1-丁醇或 3-甲基-1-丁醇中,1c 和 2c 在非常温和的条件下被还原成三芳基甲烷 Ar3C-H 3c,而在其他体积较大的醇中,1c 和 2c 则在较强的条件下被还原。在某些情况下,副产物醛或酮的形成得到了证实。化合物 1a、b、d、e 以及 2a、b 在更强的条件下发生了类似的反应。在几种醇中的反应速率按 2a < 2b < 2c 的顺序增加,2c 的醇反应速率按乙醇 > 3-甲基-1-丁醇 > 1-丁醇 > 2-丙醇 > 甲醇 > 2-丁醇 > 2-甲基-1-丙醇的顺序降低。化合物 2b、c 在四氢呋喃中也被还原,并在二甲亚砜或水中形成呫吨衍生物。