Steric control of organic transformation by a dendrimer cage: organocobalt dendrimer porphyrins as novel coenzyme B(12) mimics.
Steric control of organic transformation by a dendrimer cage: organocobalt dendrimer porphyrins as novel coenzyme B(12) mimics.
复制标题
通过树枝状聚合物笼对有机转化的空间控制：有机钴树枝状聚合物卟啉作为新型辅酶 B(12) 模拟物。
DOI：
10.1021/ja020687i
复制
发表时间：
2002
影响因子：
15
通讯作者：
T. Aida
中科院分区：
文献类型：
--
作者：
M. Uyemura;T. Aida
聚（芳基酯）树枝状聚合物卟啉（m-[Gn]TPP）Co（II）和（p-[Gn]TPP）Co（II）（n = 0-3）的钴（II）络合物在60 ℃下在CDCl（3）中在金属中心处与炔丙醇进行AIBN引发的烷基化（AIBN = 2，2 '-偶氮二（异丁腈）），其中树枝状取代基不影响总转化率，但影响烷基化的选择性。在最大的（m-[G3]TPP）Co（II）的情况下，以91%的产率选择性地形成单一的有机钴（III）物质（Co（III）-C（=CH（2））CH（2）OH，4），这是由于大树枝状聚合物笼对4的空间保护，防止另一分子的钴卟啉物质进入。相反，对于其它钴（II）卟啉，除了4之外，还形成异构化化合物，例如Co（III）-C（CH（3））=CHOH（5）和Co（III）-CH（CH（3））CHO（6）。使用AIBN-d（12）代替非氘代AIBN的（m-[G3]TPP）Co（II）的立体化学研究表明，烷基化（氢化钴（III）加成至炔丙醇）对反式加合物具有选择性。结果还表明，该加成步骤不涉及炔丙醇的外部活化。
Cobalt(II) complexes of poly(aryl ester) dendrimer porphyrins (m-[Gn]TPP)Co(II) and (p-[Gn]TPP)Co(II) (n = 0-3) underwent AIBN-initiated alkylation (AIBN = 2,2'-azobis(isobutyronitrile)) at the metal center with propargyl alcohol in CDCl(3) at 60 degrees C, where the dendritic substituents did not affect the overall conversion rate but selectivity of the alkylation. With the largest (m-[G3]TPP)Co(II), a single organocobalt(III) species (Co(III)-C(=CH(2))CH(2)OH, 4) was selectively formed in 91% yield, due to a steric protection of 4 by the large dendrimer cage from the access of another molecule of cobalt porphyrin species. In contrast, with other cobalt(II) porphyrins, isomerized compounds such as Co(III)-C(CH(3))=CHOH (5) and Co(III)-CH(CH(3))CHO (6) were formed in addition to 4. A stereochemical investigation with (m-[G3]TPP)Co(II) using AIBN-d(12), in place of nondeuterated AIBN, demonstrated that the alkylation (cobalt(III) hydride addition to propargyl alcohol) is selective to a trans adduct. Results also indicated that this addition step does not involve external activation of propargyl alcohol.