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

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]BF 4 ) 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.

Samarium Triiodide

“…8 (G) A new and facile method to prepare (Z)-allylic iodides 2 from the acetates of Baylis-Hillman adducts 1 mediated by samarium triiodide was developed in ionic liquid [bmim]BF 4 with excellent yields and good stereoselectivity. 9 (H) A novel, one-pot three-component reaction of aldehydes, a-halo ketones and (phenylsulfonyl)acetonitrile was achieved in good yields in the presence of samarium triiodide. 10 (I) SmI 3 -promoted b-elimination reactions of a-chloro-b-hydroxy ketones offer a highly efficient way to synthesize a,b-unsaturated ketones in good yields and E-diastereoselectivity.…”