HYDROBORATION .49. EFFECT OF STRUCTURE ON SELECTIVE MONO-HYDROBORATION OF REPRESENTATIVE CONJUGATED DIENES BY 9-BORABICYCLO[3.3.1]NONANE
HYDROBORATION .49. EFFECT OF STRUCTURE ON SELECTIVE MONO-HYDROBORATION OF REPRESENTATIVE CONJUGATED DIENES BY 9-BORABICYCLO[3.3.1]NONANE
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DOI：
10.1021/jo00400a007
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发表时间：
1978-01-01
影响因子：
3.6
通讯作者：
KRAMER, GW
中科院分区：
文献类型：
--
作者：
BROWN, HC;LIOTTA, R;KRAMER, GW
先前有人提出，在 1, 3-环戊二烯和 1, 3-环己二烯与二异戊基硼烷的硼氢化反应中硼所占据的位置差异可能是平面 C-5 环和褶皱 C-6 环的空间要求不同的结果。 11 相同的解释可用于 9-BBN。对于前面讨论的 2, 5-二甲基-2, 4-己二烯，末端甲基取代基的定向影响将 9-BBN 部分引导至烯丙基位置（式 4）。这里还可以控制反应以主要产生单硼氢化产物。有人建议，进一步的硼氢化反应将被阻止，因为它会将第二个 9-BBN 部分置于拥挤的相邻位置。可能相同的解释也适用于环己烯基中间体（eq 8）。不管该现象的精确解释如何，事实是反应很容易干净地进行，得到烯丙基衍生物。此类烯丙基衍生物具有很强的反应性，很容易加成到醛和酮的羰基上。 13最近，我们合成了一系列结构为l-芳基-l-(A2-环己烯基)乙醇的叔醇。显然，将1-氯-或1-溴-2-环己烯转化成相应的格氏试剂是不可行的。通过用 9-BBN 加合物（eq 9）处理相应的苯乙酮衍生物，成功完成了合成。 15
It was previously suggested that this difference inthe po-sition taken by boron in the hydroboration of 1, 3-cyclopentadiene and 1, 3-cyclohexadiene with disiamylborane might be the result of differences in the steric requirements of the planar C-5 ring and the puckered C-6ring. 11 The same ex-planation may be utilized for 9-BBN. In the case of 2, 5-dimethyl-2, 4-hexadiene, discussed earlier, the directive influence of the terminal methyl substituents directs the 9-BBN moiety to the allylic position (eq 4). Here the reaction can also be controlled to yield the monohydroboration product predominantly. It was suggested that further hydroboration would be resisted since it would place the second 9-BBN moiety in thecrowded adjacent position. Possibly the same explanation may hold for the cyclohexenyl intermediate (eq 8). Irrespective of the precise explanation of the phenomenon, the fact is that the reaction readily pro-ceeds cleanly to give the allylic derivative. Such allylic deriv-atives are quite reactive, readily adding to the carbonyl group of aldehydes and ketones. 13Recently, we had occasion to synthesize a series of tertiary alcohols with thestructure l-aryl-l-(A2-cyclohexenyl) etha-nol. Apparently, it is not feasible to convert 1-chloro-or 1-bromo-2-cyclohexene into the corresponding Grignard re-agents. The synthesis was successfully accomplished by treating the corresponding acetophenone derivatives with the 9-BBN adduct (eq 9). 15