Air- and Water-Tolerant Rare Earth Guanidinium BINOLate Complexes as Practical Precatalysts in Multifunctional Asymmetric Catalysis

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• 作者：Jerome R. Robinson ; Xinyuan Fan ; Jagjit Yadav ; Patrick J. Carroll ; Alfred J. Wooten ; Miquel A. Peric脿s ; Eric J. Schelter ; Patrick J. Walsh
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：June 4, 2014
• 年：2014
• 卷：136
• 期：22
• 页码：8034-8041
• 全文大小：514K
• 年卷期：v.136,no.22(June 4, 2014)
• ISSN：1520-5126

文摘

Shibasaki鈥檚 REMB catalysts (REMB; RE = Sc, Y, La鈥揕u; M = Li, Na, K; B = 1,1鈥?bi-2-naphtholate; RE/M/B = 1/3/3) are among the most enantioselective asymmetric catalysts across a broad range of mechanistically diverse reactions. However, their widespread use has been hampered by the challenges associated with their synthesis and manipulation. We report here the self-assembly of novel hydrogen-bonded rare earth metal BINOLate complexes that serve as bench-stable precatalysts for Shibasaki鈥檚 REMB catalysts. Incorporation of hydrogen-bonded guanidinium cations in the secondary coordination sphere leads to unique properties, most notably, improved stability toward moisture in solution and in the solid state. We have exploited these properties to develop straightforward, high-yielding, and scalable open-air syntheses that provide rapid access to crystalline, nonhygroscopic complexes from inexpensive hydrated RE starting materials. These compounds can be used as precatalysts for Shibasaki鈥檚 REMB frameworks, where we have demonstrated that our system performs with comparable or improved levels of stereoselectivity in several mechanistically diverse reactions including Michael additions, aza-Michael additions, and direct Aldol reactions.