N,N′‐Dioxide/Nickel(II)‐Catalyzed Asymmetric Inverse‐Electron‐Demand Hetero‐Diels–Alder Reaction of β,γ‐Unsaturated α‐Ketoesters with Enecarbamates |
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| Authors: | Yuhang Zhou Yin Zhu Dr Lili Lin Yulong Zhang Jianfeng Zheng Prof Dr Xiaohua Liu Prof Dr Xiaoming Feng |
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| Affiliation: | Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064 (China), Fax: (+86)?28‐85418249 |
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| Abstract: | N,N′‐Dioxide/nickel(II) complexes have been developed to catalyze the inverse‐electron‐demand hetero‐Diels–Alder reaction of β,γ‐unsaturated α‐ketoesters with acyclic enecarbamates. After detailed screening of the reaction parameters, mild optimized reaction conditions were established, affording 3,4‐dihydro‐2H‐pyranamines in up to 99 % yield, 99 % ee and more than 95:5 d.r. The catalytic system was also efficient for β‐substituted acyclic enecarbamates, affording more challenging 2,3,4‐trisubstituted 3,4‐dihydro‐2H‐pyranamine with three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities. The reaction could be scaled up to a gram scale with no deterioration of either enantioselectivity or yield. Based on these experiments and on previous reports, a possible transition state was proposed. |
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| Keywords: | asymmetric catalysis cycloaddition Diels– Alder reaction N N′ ‐dioxides nickel |
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