Remarkable rate acceleration of SmI3-mediated iodination of acetates of Baylis-Hillman adducts in ionic liquid: facile synthesis of (Z)-allyl iodides

摘要

Stereoselective transformation of Baylis-Hillman acetates 1 into corresponding Z)-allyl iodide%29&ck%5B%5D=abstract&ck%5B%5D=keyword'>(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 iodide%29&ck%5B%5D=abstract&ck%5B%5D=keyword'>(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.