Journal of Organic Chemistry p. 6468 - 6483 (1995)
Update date:2022-09-26
Topics:
Ren, Xiao-Feng
Turos, Edward
Lake, Charles H.
Churchill, Melvyn Rowen
The regiochemistry and stereochemistry for the halocyclization reactions of unsaturated benzyl sulfides have been examined as a function of tether length, type of unsaturation (carbon-carbon double bond versus carbon-carbon triple bond), substituents, and halogenating agent.Alkenyl sulfides were found to react with iodine or bromine at room temperature to give five-membered ring cycloadducts exclusively over those having four-membered rings, while for larger systems, six-membered ring products are formed preferentially over their five-membered ring isomers and exclusively over the seven-membered ring adducts.The endo- versus exo-regioselectivity of these alkenyl sulfide ring closure most likely reflects the difference in thermodynamic stabilities of the β-halo sulfide cycloadducts, which are able to equilibrate via a common episulfonium intermediate.The efficiency of cyclization process markedly drops off for these alkenyl sulfides as the tether length increases beyond four intervening carbon centers.Thus, while the halogenations of 3-butenyl sulfides and 4-pentenyl sulfides give high yields of cycloadducts, those of 5-hexenyl sulfides afford only small amounts of cyclized products and large quantities of acyclic dibromides.Conversely, the reactions of acetylenic sulfides with iodine give uniformly high yields and regiochemical control regardless of the tether length.Thus, 3-butynyl and 4-pentynyl sulfides cyclize cleanly to the five-membered ring while 5-hexynyl sulfides give exclusively the six-membered ring.The products arising from these alkynyl sulfide ring closures are believed to be formed under kinetic control.The methodology has been applied to the synthesis of unusual bicyclic β-lactams related to the penicillin family of antibiotics.
View MoreChangde Yungang Biotechnology Co., Ltd
website:http://www.cdyg.com
Contact:+86-736-7391178
Address:Qiaonan Industrial Park, Changde City, Hunan Province
He Bei Shun Er Chemical Co., LTD.
Contact:86-0311-86996932/86860168
Address:No 18,North street
Beijing Green Guardee Technology CO,.LTD
Contact:+86-10-69706062
Address:F2 BLdj,5 No.37 Chaoqian Road
Cangzhou Senary Chemical Science-tech Co., Ltd
Contact:+86-317-3563899, 3563699
Address:168 Jinde Road, Cangzhou, Hebei, China
Jiangxi Hito Chemical Co., Ltd.
Contact:+86-792-3170318
Address:No. 6, Tianhong Ave., Xinghuo Industry Park, Yongxiu, Jiujiang, Jiangxi, China
Doi:10.1039/a607384k
(1997)Doi:10.1016/j.tetlet.2004.09.120
(2004)Doi:10.1007/BF00508676
(1984)Doi:10.1002/ardp.19673000312
(1967)Doi:10.1016/j.carres.2004.08.008
(2004)Doi:10.1246/cl.1981.1409
(1981)