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Remarkable rate acceleration of SmI3-mediated iodination of acetates of Baylis-Hillman adducts in ionic liquid: facile synthesis of (Z)-allyl iodides |
Liu Yun-Kui, Zheng Hui, Xu Dan-Qian, Xu Zhen-Yuan, Zhang Yong-Min |
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, China; Department of Chemistry, Zhejiang University, Hangzhou 310028, China |
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Abstract Stereoselective transformation of Baylis-Hillman acetates 1 into corresponding (Z)-allyl iodides 2 has been achieved by treatment of 1 with samarium triiodide in THF. Remarkable rate acceleration of samarium triiodide-mediated iodination of 1 was found when ionic liquid 1-n-butyl-3-methyl-imidazolium tetrafluroborate ([bmim]BF4) was used as reaction media in stead of THF. This novel approach proceeds readily at 50 °C within a few minutes to afford (Z)-allyl iodides 2 in excellent yields. A mechanism involving stereoselective iodination of the acetates of Baylis-Hillman adducts by samarium triiodide is described, in which a six-membered ring transition state played a key role in the stereoselective formation of 2.
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Received: 21 November 2005
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