The preparation and some properties of 2-methyl-1-propene-1-boronic acid
The preparation and some properties of 2-methyl-1-propene-1-boronic acid
复制标题
DOI：
10.1021/jo50013a019
复制
发表时间：
1953-07
影响因子：
3.6
通讯作者：
R. Letsinger;I. Skoog
中科院分区：
文献类型：
--
作者：
R. Letsinger;I. Skoog
虽然已经制备了相当多的烷基-和芳基-硼酸（1），但仅描述了两种烯基硼酸类型的化合物。第一种产物是β-苯乙烯基硼酸（2），由β-苯乙烯基溴化镁与硼酸异丁酯反应制得;第二种产物是2-氯代乙烯基硼酸（3），由三溴化硼（或三溴化硼）与乙炔催化加成，然后水解制得。这一领域的工作受到限制，因为除了苯乙烯基镁和苯乙烯基锂化合物之外，经典合成方法中所需的烯基金属化合物还没有得到。随着Braude和Timmons（4）最近的发现，烯基锂试剂可以通过锂与烯基溴的作用来制备，然而，这种制备不饱和硼酸的路线已经成为可能。为了获得有关这一方法可行性的信息，我们研究了由异丁烯基锂和硼酸甲酯制备2-甲基-1-丙炔基-1-硼酸的方法，得到了满意的产率（60-79%），它与二氧化碳反应得到α-甲基巴豆酸（重结晶后产率为27%）。然而，与硼酸甲酯的反应不如用于制备烷硼酸的类似反应令人满意。约翰逊和同事（5）从丁基溴化镁与硼酸甲酯的反应中以50%的产率（重结晶前产率为60-70%）分离出纯丁烷硼酸。我们能够重复他们的结果，而且发现丁基锂可以令人满意地代替格氏试剂。然而，由异丁烯基锂与硼酸甲酯的反应实现的纯化的2-甲基-1-丙炔-1-硼酸的最佳产率为7%（重结晶前为22%）。2-甲基-1-丙炔-1-硼酸，mp 84-86，在223 µ（e= 1.25）处显示最大吸收。
Although a considerable number of alkyl-and aryl-boronic acids have been prepared (1), only two compounds of the alkenylboronic acid type have been described. The first to be reported, ß-styreneboronic acid (2), was obtained from a reaction of ß-styrylmagnesium bromide with isobutyl borate, and the second, 2-chloroethyleneboronic acid (3), was formed by the catalyzed addition of boron trichloride (or boron tribromide) to acetylene, followed by hydrolysis. Work in this general field has been limited by the fact that alkenylmetallic compounds necessary for use in the classical synthetic procedurehave, with the exception of the ß-styryl-magnesium and-lithium compounds, been unavailable. With the recent discovery by Braude and Timmons (4), that alkenyllithium reagents can be prepared by the actionof lithium on alkenyl bromides, however, this route for the preparation of the unsaturated boronic acids has been made possible. In order to obtaininformation concerning the feasibility of this procedure we have investigated the preparation of 2-methyl-l-propene-l-boronic acid from iso-butenyllithium and methyl borate.Isobutenyllithium was obtained in satisfactory yield (60-79%) without difficulty, and it reacted with carbon dioxide to give ß-methylcrotonic acid (27% yield after recrystallization). The reaction with methyl borate, however, was less satisfactory than the analogous reactions used for the preparation of the alkaneboronic acids. Johnson and coworkers (5) isolated purebutaneboronic acid in 50% yield (60-70% yield before recrystallization) from a reaction of butyl-magnesium bromide with methyl borate. We were able to duplicate their results, and furthermore, found that butyllithium could be used satisfactorily in place of the Grignard reagent. Yet the best yield of purified 2-methyl-l-propene-l-boronic acid that was realized from a reaction of isobutenyllithium with methyl borate was 7%(22% before recrystallization). 2-Methyl-l-propene-l-boronic acid, mp 84-86, shows an absorption maxi-mum at 223 µ (e=