N,O-Chelating Four-Membered Metallacyclic Titanium(IV) Complexes for Atom-Economic Catalytic Reactions

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• 作者：Scott A. Ryken ; Laurel L. Schafer
• 刊名：Accounts of Chemical Research
• 出版年：2015
• 出版时间：September 15, 2015
• 年：2015
• 卷：48
• 期：9
• 页码：2576-2586
• 全文大小：604K
• ISSN：1520-4898

文摘

Titanium, as the second most abundant transition metal in the earth鈥檚 crust, lends itself as a sustainable and inexpensive resource in catalysis. Its nontoxicity and biocompatibility are also attractive features for handling and disposal. Titanium has excelled as a catalyst for a broad range of transformations, including ethylene and 伪-olefin polymerizations. However, many reactions relevant to fine chemical synthesis have preferrentially employed late transition metals, and reactive, inexpensive early transition metals have been largely overlooked. In addition to promising reactivity, titanium complexes feature more robust character compared with some other highly Lewis-acidic metals such as those found in the lanthanide series. Since the advent of modulating ligand scaffolds, titanium has found use in a growing variety of reactions as a versatile homogeneous catalyst. These catalytic transformations include hydrofunctionalization reactions (adding an element鈥揾ydrogen (E鈥揌) bond across a C鈥揅 multiple bond), as well as the ring-opening polymerization of cyclic esters, all of which are atom-economic transformations.