釕金屬丙二烯錯合物的分子內Diels-Alder反應

Intramolecular Diels-Alder Reactions Mediated by Ruthenium Vinylidene Complexes

張書豪(Shu-Hao Chang)

指導教授 ： 林英智

國立臺灣大學/理學院/化學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00992

摘要

探討一系列含有環戊二烯釕金屬亞乙烯基錯合物的合成與反應性，陽離子的釕金屬亞乙烯基錯合物 [Ru]=C=CHCH(R)CH2CH=CH2 ([Ru] = CpRu(PPh3)2; 2a, R = para-C6H4-Ph; 2b, R = para-C6H4-F; 2c, R = naphthyl; 2d, R = ortho- C6H4-OCH2CH=CH2; 2e, R = ortho-C6H4-OCH2C6H5Ph; 2f, R = 9-Cl-10-anthracenyl) 可以藉由 (η5-C5H5)(PPh3)2Ru-Cl 與各式不同種類的 1,5-enyne 合成所得到。錯合物 2a 在氯仿中會轉換成 ([Ru]=C=CHCH2CH(R)CH=CH2) (3a) 經由骨架重排的過程而得到混合物 2a 和 3a，且 2a 和 3a 的比例接近2:1，並非完全轉換成產物 3。當有拉電子基在錯合物 2b 時，會加速骨架重排的過程；但當有推電子基在錯合物 2a 時，則會使骨架重排的過程變慢，但最後混合物的比例仍然維持將近2:1。
錯合物 2a 具有一個苯環在Cγ 上，其立體阻礙比具有兩個苯環在 Cγ上的錯合物 [Ru]=C=CHC(Ph)2CH2CH=CH2小的許多，且後者同樣也會發生骨架重排的反應並完全轉換形成產物。因此，可得知立體阻礙效應會明顯的影響錯合物由 2(2a ~ 2e) 轉變為 3 (3a ~ 3e) 的反應平衡。
錯合物2f (R = 9-Cl-10-anthracenyl)與甲醇鈉反應會生成錯合物[Ru]-C≡C-CH(R)CH2CH=CH2 (4f)，而錯合物 4f 在室溫中與丙烯基碘會經由分子內Diels-Alder 過程生成錯合物 6f。分子內 Diels-Alder 反應提供了一個在溫和條件下直接合成多環的方法，且提供很好的立體選擇性，只有 RS 和 SR 兩種立體異構物會生成。
在本篇論文中，分子內 Diels-Alder 過程只發生在 Cß 的丙烯基與多環芳烴 PAH 之間，卻不會發生在 Cγ 的丙烯基與多環芳烴 PAH 之間。研究不飽和碳鍵與多環芳烴之間長度上的變化，將如何影響分子內 Diels-Alder 是非常有趣的。本篇論文合成了出不同長度的碳鏈連接不飽和鍵，例如：錯合物 3fa 和錯合物 3fd 。錯合物 3fa 及 3fd 是由釕金屬亞丙二烯基和不同的 Grignard 試劑合成所得，將 1-(anthracen-9-yl)prop-2-yn-1-ol 與 CpRu(PPh3)2Cl 反應在含有KPF6 的二氯甲烷溶液中可得到釕金屬亞丙二烯基合錯合物 2fa。
錯合物 2fa 再與溴化乙炔基鎂反應得到釕金屬錯合物 3fa ，錯合物 3fa相較於錯合物 4f其三鍵與多環芳烴 PAH 之間有著較短的距離，其在Cγ的丙烯基與多環芳烴 PAH 之間的距離較長，我們沒有觀察到任何分子內 Diels-Alder 反應發生。
若將錯合物 2fa 再與 but-3-enylmagnesium bromide 反應則得到釕金屬錯合物 3fd ，在錯合物 3fd 中其雙鍵與多環芳烴 PAH 之間有著較長的距離相較於錯合物 4f 。然而沒有任何的分子內 Diels-Alder 反應發生在錯合物 3fd 。更進一步來說，錯合物 3fa 在室溫中與丙烯基碘反應會經由分子內 Diels-Alder 反應生成錯合物 5fa ，這似乎說明這分子內 Diels-Alder 反應只發生在 Cß 的丙烯基與多環芳烴PAH之間 。

關鍵字

釕金屬 ； 亞乙烯基 ； 環化反應 ； 重排反應 ； Diels-Alder 反應

並列摘要

The reactivity of a series of cationic ruthenium vinylidene complexes containing the cyclopentadienyl phosphine ligand are studied. Cationic metal vinylidene complexes [Ru]=C=CHCH(R)CH2CH=CH2 ([Ru] = CpRu(PPh3)2; 2a, R = para-C6H4-Ph; 2b, R = para-C6H4-F; 2c, R = naphthyl; 2d, R = ortho- C6H4-OCH2CH=CH2; 2e, R = ortho-C6H4-OCH2C6H5Ph; 2f, R = 9-Cl-10-anthracenyl) are prepared from the reaction of (η5-C5H5)(PPh3)2Ru-Cl with different 1,5-enyne. Complex 2a in chloroform transforms into [Ru]=C=CHCH2CH(R)CH=CH2 3a via a metathesis process giving the mixture of 2a and 3a in a ratio approximately 2:1. Electron withdrawing group on complex 2b makes metathesis process faster than that in 2a with an electron donating group. But the ratio of 2b and 3b didn’t changed. Complex 2a with only one phenyl group on Cγ has less steric effect than the vinylidene complex [Ru]=C=CHC(Ph)2CH2CH=CH2 having two phenyl groups on Cγ which could transforms into the metathesis product completely in our previously report. Therefore, the metathesis reaction was affected by the steric effect.
Complex 2f (R = 9-Cl-10-anthracenyl) reacts with sodium methoxide to yield [Ru]-C≡C-CH(R)CH2CH=CH2 (4f). Complex 4f is treated with allyl iodide at room temperature giving the complex 6f via an intramolecular Diels-Alder process. This intramolecular Diels-Alder reaction provides a direct approach to complex polycyclic compounds under remarkably mild conditions. This reaction also gives very high diastereoselectivity. Only RS and SR form can be obtained. This intramolecular Diels-Alder reaction takes place only between the allyl group on Cß and the anthracenyl group. However, no intramolecular Diels-Alder reaction could be observed between the allyl group on Cγ and the anthracenyl group. It is interesting to explore how the intramolecular process is affected by the length of the spacer linker. With various length of the spacer linker, complexes 3fa and 3fd could be synthesized by the allenylidene complex with different Grignard agents. Reaction of 1-(anthracen-9-yl)prop-2-yn-1-ol with CpRu(PPh3)2Cl in the presence of KPF6 in CH2Cl2 afforded the cationic ruthenium allenylidene complex 2fa. Complex 2fa was treated with ethynylmagnesium bromide to afford the ruthenium acetylide complex 3fa, which has shorter distance between triple bond and the anthracenyl group than the distance between double bond on allyl group and the anthracenyl group in complex 4f. Complex 2fa was treated with but-3-enylmagnesium bromide to afford the ruthenium acetylide complex 3fd, which has longer distance between double bond on but-3-enyl and the anthracenyl group than the distance between double bond on allyl group and the anthracenyl group in complex 4f. However, there is no intramolecular Diels-Alder product observed in 3fa and 3fd. Furthermore, when complex 3fa is also treated with allyl iodide at room temperature, the intramolecular Diels-Alder product 5fa could be observed. It seems that the Diel-Alder reaction takes place only between the anthracenyl group and the allyl group on Cß.

並列關鍵字

ruthenium ； vinylidene ； cyclization ； rearrangement ； Diels-Alder

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