金屬紫質咪唑鹽合成及氧化催化反應之研究

利用離子液體及金屬紫質催化性質之特性，合成一系列IL(TPP)-M與吡咯環beta-位置置換成氯基團的IL(TPP)Cl8-M (M = Fe, Co, Ni及Mn)。氯取代的金屬紫質可穩定中心金屬，並且可增加其氧化還原電位，藉此，可降低HOMO-LUMO能階，並期望能增加氧轉移之活性。金屬紫質咪唑鹽於烯類的氧化催化反應上，若與NHPI及異丁醛(isobutyraldehyde)共催化，可在室溫進行環氧化反應，反應溶劑選擇具有弱配位能力的乙腈，則可獲得較佳結果。而催化劑則以IL(TPP)Cl8-Fe，相較於其他金屬，可得較高的催化活性，但此系統之催化劑，無法回收再使用。在微波照射下，可製備不同官能基之咪唑鹽離子液體，此可選擇作為金屬紫質咪唑鹽，進行化合物的催化氧化之溶劑。烯類的氧化，條件於50psi的氧氣壓力，70-80 度反應溫度下，以IL(TPP)Cl8-M及NHPI共催化，並於[C3CNbmim][Br]，會進行氧化斷裂反應 (Oxidative cleavage)。催化測試中，以alpha-甲基苯乙烯經由IL(TPP)Cl8-Fe進行催化，可得較佳的結果，而催化劑經由回收再利用數次，仍保持良好催化性，進而達到其回收再利用之效益。更進一步利用此系統之結果，也可成功的進行其他烯類氧化反應。烷類芐基取代（Benzylic Group）的氧化，則以IL(TPP)Cl8-Mn進行催化，無論助催化劑NHPI加入與否，均可將其芐基取代羰基化，於苯乙烷的氧化測試中，反應後的催化劑，亦可回收處理，再利用數次，仍保持良好催化性。然而，紫質中心為其它金屬，則催化活性均不佳，利用上述最佳之結果，也可成功進行其他烷類氧化反應。醇類氧化成醛或酮的反應上，以IL(TPP)Cl8-Co溶於[C3CNbmim][Br]，可獲得最佳催化結果，然而，反應需要助催化劑NHPI，作為自由基起始劑來源，才能進行氧化，而反應後的催化劑，亦可回收使用。另外，若此反應再加入異丁醛與之共催化，則會造成催化劑降解。於高壓氧氣或是微波照射下，也可成功利用IL(TPP)Cl8-Fe與異丁醛共催化，進行2,4-二叔丁基苯酚的耦合催化反應。

關鍵字

紫質；離子液體；金屬紫質咪唑鹽；氧化；催化

並列摘要

To take advantage of ionic liquid and the catalytic properties of porphyrin, we have synthesized a series of metalloporphyrin imidazolium salts IL(TPP)-M and beta- chloro-substituted IL(TPP)Cl8-M [M = Fe, Co, Ni and Mn]. The chloro-substituted metalloporphyrin would fine-tune the property of metal ions, in particular the redox potential, which decreases HOMO-LUMO the energy gap and hope to increase the activity of oxygen transfer. Oxidation of alkenes catalyzed by metalloporphyrin imidazolium salts in the presence of N-hydroxyphthalimide (NHPI) and isobutyraldehyde as co-catalysts provided the epoxidation product at room temperature. And the solvent with a weak coordinating ability such as acetonitrile gave the best result. It appeared that (IL(TPP)Cl8-Fe) is more active than the corresponding Co(II), Mn(III), and Ni(II) species. However, this catalytic system could not be re-cycled. With the microwave irradiation, we have developed a method to prepare the functionalized imidazolium salts, which become as a good medium for the reaction catalyzed by metalloporphyrin imidazolium salts. Thus, the oxidation of alkenes catalyzed by IL(TPP)Cl8-M and NHPI under 50 psi of O2 at 70-80 degree C in [C3CNbmim][Br] gave the oxidative cleavage product. For example, the catalytic system consisted with IL(TPP)Cl8-Fe and [C3CNbmim][Br] illustrated a quantitative production of acetophenone from the oxidative cleavage of alpha-metylstyrene. Furthermore, this catalytic system could be recycled and used for several times without loss of any activity. For the oxidation of benzylic substrates, IL(TPP)Cl8-Mn did catalyze the oxidation to form phenyl ketones even without the use of NHPI. The catalyst can also be re-used for several times in the conversion of ethylbenzene into acetophenone. Other metal complexes exhibited less activity as compared to IL(TPP)Cl8-Mn. In the oxidation of alcohols to aldehydes or ketones, IL(TPP)Cl8-Co appeared to be the best catalyst. However, it did require the assistance of NHPI, acting as the radical initiator to carry out the oxidation. On the other hand, the use of isobutyraldehyde would cause the decomposition of porphyrin complex. The mixture of [C3CNbmim][Br] and IL(TPP)Cl8-Co used as a catalytic system, in the presence of oxygen (50 psi), showed good activity for oxidation of alcohols into the corresponding carbonyl compounds. Moreover, this mixture can be re-cycled and used.

並列關鍵字

metalloporphyrin ； ionic liquid ； oxidation ； imidazolium salt ； catalyzed

參考文獻

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金屬紫質咪唑鹽合成及氧化催化反應之研究

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