在有機分子的結構上，碳-碳單鍵的形成是很多重要的合成步驟當中的一種。在過去30年來，藉由使用醋酸錳(Ⅲ)來進行氧化性自由基反應已經可以成功地形成碳-碳單鍵。特別是經由分子間或分子內的自由基加成或環化反應，在有機化學上已經成為一種有趣的議題去討論反應位置或立體選擇性的關係。
藉著使用B3LYP/6-31G*的方法，去研究α-烷基-β-酮基酯類自由基的環化反應，結果顯示順式-異構物自由基中間體的活化能會比相對應的反式-異構物自由基中間體的活化能還要來的低大約2.0 kcal/mol，而且反式-異構物自由基中間體通常是比順式-異構物自由基中間體還要來的穩定。然而，實驗結果顯示出有一些環化產生順式-異構物當主產物，但是有一些則不是。α-烷基-β-酮基酯類的氧化性自由基環化是使用2當量的醋酸錳(Ⅲ)來產生外向-環化產物。而不是產生內向-環化產物。當α-烷基-β-酮基酯類使用醋酸錳(Ⅲ)來進行氧化性自由基的環化反應，若產生一級的自由基中間體，則會伴隨著快速地抓取一個氫原子，也就是引起環化反應的是屬於動力學控制，而且順式-異構物是主產物。另一方面，當α-烷基-β-酮基酯類使用醋酸錳(Ⅲ)來進行氧化性自由基的環化反應，若產生二級的苯基或三級的自由基中間體時，則會伴隨著速度較慢的，藉由醋酸錳(Ⅲ)再取一步的氧化自由基，所以引起環化反應是屬於熱力學控制，而且以反式-異構物是主產物。

Carbon-carbon bond formation is one of the most important synthetic steps in construction of organic molecules. In the past 30 years, it has been increasingly achieved by Mn(OAc)3–based oxidative free-radical reaction. Especica-lly, Free- radical addition or cyclization th-rough inter- or intra- molecular reaction has become an interesting topic for region- or ste-reo-selectivity.
The cyclization of α-alkyl-β-ketoester radicals was studied at level of B3LYP/6-31G* and the results showed that activation energies to cis-isomer radical intermediates are ca. 2 kcal/mol smaller than those to the corresponding trans-isomer radical intermediates and the trans-iso-mer radical intermediates are usually more sta-ble than the cis-isomer radical intermediates. However, the experimental results showed that some of the cyclizations produced cis-isomer as a major product, but some didn’t.Oxidative cyc-lizations of the α-alkyl-β-ketoester 5 with 2 equivalent of Mn(OAc)3 generated exo-cyclization products, instead of endo-cyclization products. When the oxidative cyclization of the α-alkyl-β-ketoester 5 with Mn(OAc)3 generates primary radical intermediates, followed by faster hydrogen abstraction, that causes the cycliza-tion to be kinetic-control and the major product is cis-isomer. On the other hand, when the oxidative cyclization of the α-alkyl-β-ketoester 5 with Mn(OAc)3 generates tertiary or secondary benzyl radical intermediates, followed by slower further oxidation by Mn(OAc)3, that causes the cyclization to be thermodynamic-control and the major product is trans-isomer.

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