A mechanistic dichotomy in ruthenium-catalyzed propargyl alcohol reactivity: a novel hydrative diyne cyclization.
A mechanistic dichotomy in ruthenium-catalyzed propargyl alcohol reactivity: a novel hydrative diyne cyclization.
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钌催化的炔丙醇反应性的机械二分法：一种新型的水合二炔环化。
DOI：
10.1021/ja036410f
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发表时间：
2003
影响因子：
15
通讯作者：
Rudd,MichaelT
中科院分区：
文献类型：
--
作者：
Trost,BarryM;Rudd,MichaelT
[CpRu（CH_3CN）_3] PF_6催化二炔醇环化异构化生成2-乙烯基-1-酰基环烯烃的反应是通过叔醇或仲醇的电离和再电离的双烯环戊二烯进行的。在伯醇的情况下，其中水首先加入的竞争途径似乎会发生。在水存在下的二炔反应中测试了这一拟议次要途径的可行性。非常令人兴奋的是，在加入水的情况下发生环化反应以形成1-酰基环烯烃。这被证明是形成五元环和六元环的一般过程。有趣的是，Z-5-癸烯-2，8-二炔水合环化为1-乙酰基-2-乙基-环己-1，4-二烯时双键没有异构化。此外，相同底物的环氧化物环化而不打开应变环氧化物。不对称取代的二炔以显著的化学选择性环化，其中水攻击较少受阻的炔。任何种类的β分支都只能得到一个产物。值得注意的是，即使是甲基与乙基的竞争，在有利于水加成到带甲基的炔中时，仍然产生2.5：1的选择性。醇可以取代水并提供烯醇醚。强有力的机械证据表明，两个反应歧管确实操作，这取决于炔丙醇的存在和羟基轴承碳上的取代度。
The cycloisomerization of diyne-ols catalyzed by [CpRu(CH3CN)3]PF6to 2-vinyl-1-acylcycloalkenes proceeds via a ruthenacyclopentadiene involving initial ionization of the tertiary or secondary alcohol, followed by readdition. In the case of primary alcohols, a competing pathway wherein water first adds would appear to occur. The feasibility of this proposed minor pathway was tested in the reaction of diynes in the presence of water. Quite excitingly, cyclization comcommittant with addition of water to form 1-acylcycloalkenes occurs. This proves to be general process to form five- and six-membered rings. Interestingly, hydrative cyclization ofZ-5-decen-2,8-diyne to 1-acetyl-2-ethyl-cyclohexa-1,4-diene occurs without isomerization of the double bonds. Furthermore, the epoxide of the same substrate cyclizes without opening of the strained epoxide. Unsymmetrically substituted diynes cyclize with remarkable chemoselectivity wherein water attacks the less hindered alkynes. β-branching of any kind gives only a single product. Remarkably, even competing methyl versus ethyl still effects a 2.5:1 selectivity in favoring water addition to the methyl-bearing alkyne. Alcohols can replace water and provide enol ethers. Strong mechanistic evidence suggests two reaction manifolds indeed operate, depending upon the presence of propargyl alcohols and the degree of substitution on the hydroxyl-bearing carbon.