鈷金屬錯合物催化有機磺酸酯與共軛烯類之還原偶合反應

Cobalt-Catalyzed Reductive Coupling of Organic Triflates and Tosylates with Conjugated Alkenes

朱怡樺(Yi-Hua Chu)

指導教授 ： 鄭建鴻

國立清華大學/理學院/化學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00145

摘要

利用Co 金屬催化有機三氟磺酸酯化合物及甲苯基磺酸酯化合物與共軛烯類在水、鋅粉及丙烯腈為溶劑的條件下，以外溫為80℃反應10-24小時，得到高產率的還原偶合產物。此反應除了可以使芳香性三氟甲基磺酸酯與共軛烯類進行反應，另一方面用在一級或二級的烷基磺酸酯與各種不同的共軛烯類，如丙烯酸丁酯、acrylonitrile、methyl vinyl ketone 以及phenyl vinyl sulfone也都可以成功的利用此方法合成出還原偶合產物。在反應機構的部份，推測是藉由Co(I)與Co(III) 的中間體進行催化循環步驟，與一般鈷金屬反應機構不大相同，反應先由鋅粉還原鈷金屬成一價，再經由氧化加成步驟成為三價，接著雙鍵的嵌入 (insertion)，最後再和鋅粉進行金屬交換 (transmetalation) 與水的質子化 (protonation)，進而得到還原偶合產物。

關鍵字

鈷金屬催化 ； 還原偶合反應

並列摘要

An efficient cobalt-catalyzed reductive coupling reaction of organic triflates and tosylates with electron-withdrawing alkenes (CH2=CR1EWG, EWG = electron-withdrawing group) in the presence of water and zinc powder in acetonitrile for 10 to 24 hours to give the corresponding Michael-type addtiton product (RCH2CR1EWG) was described. The methodology is versatile such that unactivated primary, secondary alkyl triflates and tosylates and various conjugated alkenes including acrylates, acrylonitrile, methyl vinyl ketone and phenyl vinyl sulfone all successfully participate in this coupling reaction. It is a unique method employing CoI2(dppe) or CoI¬2(PPh3)2, zinc and alkyl triflates and tosylates, affording conjugate addition products in high yields. Mechanistically, the catalytic reaction is likely to be initiated by the reduction of Co(II) to Co(I) by zinc power and followed by oxidative addition of organic triflates and tosylates to give Co(III) intermediate. The coordination followed by insertion of double bond to the Co center and then transmetalation of the latter with the zinc generates zinc intermediate. Protonation of this zinc intermediate with water forms the final reductive coupling product.

並列關鍵字

Cobalt-Catalyzed ； Reductive Coupling

參考文獻

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