叔丁基二甲硅氧基苯硼酸及羟基苯硼酸的制备

以邻、间、对三种溴酚为原料, 经叔丁基二甲基氯硅烷保护酚基后制成格氏试剂, 然后与硼酸酯反应, 选择性水解得到了邻、间、对-叔丁基二甲硅氧基苯硼酸, 收率分别为51%, 44%和40%. 将对位、间位的硼酸酯中间体3a, 3b用强酸水解可得到间羟基苯硼酸(产率65%)和对羟基苯硼酸(产率14%), 但发现它们极难纯化, 这是由于羟基硼酸极易生成苯二酚之故.

Preparation of t-Butyldimethylsiloxyphenyl Boronic Acids and Hydroxyphenylboronic Acids

p-, m- and o-bromophenols were first protected by t-butyldimethylchlorosilane, and then treated with Mg to form Grignard reagents. After reaction with tributylborate and selective hydrolysis, three t-butyldimethylsiloxy phenylboronic acids were obtained in yields 51% (p), 44% (m) and 40% (o), respec- tively. If dibutyl p- or m-siloxyphenylborate intermediates were hydrolyzed in strong acid, p or m-hydroxy- phenylboronic acids were achieved with yields of 14% and 65% respectively. But these hydroxyphenylbo- ronic acids were difficult to purify because the impurity hydroxyphenol was always formed spontaneously.