Studies on the factors controlling the stereoselectivity in electrophilic iodocyclization of alkylidenecyclopropyl ketones
作者:Jie Chen、Lianghua Lu、Shengming Ma
DOI:10.1016/j.tet.2008.06.060
日期:2008.9
An efficient electrophilic iodocyclization of alkylidenecyclopropyl ketones with N-iodosuccinimide (NIS) or l(2) in aqueous CH3CN affording 3-oxabicyclo[3.1.0]hexan-2-ols is described. NIS is a better electrophilic iodocyclization reagent than l(2). Four chiral centers were formed within one step. The stereochemistry was established by the X-ray diffraction studies of compounds 2e-2h, 2n, and 2c. It is quite interesting to observe that the substituent of the cyclopropane ring plays an important role in determining the relative stereochemistry at the 4-position: with R-2 being an acyl or ester group a mixture of (1S*,2R*,4S*5R*)-2 (major) and (1R*,2R*,4R*,5R*)-2 (minor) was formed with moderate selectivity while the reaction of the substrates with R being sulfonyl and p-methylphenylsulfonyl or R-1 being phenyl afforded (1R*,2R*,4S*,5S*)-2 or (1S*,2R*,4S*,5R*)-2f as the only product. The reaction is general for a range of different substrates to afford the products in moderate to high yields. (C) 2008 Elsevier Ltd. All rights reserved.
Catalytic Regioselectivity Control in Ring-Opening Cycloisomerization of Methylene- or Alkylidenecyclopropyl Ketones
作者:Shengming Ma、Lianghua Lu、Junliang Zhang
DOI:10.1021/ja0494860
日期:2004.8.1
hydrogenated or hydroborated to afford new heterocyclic products stereoselectively. These three types of differentreactions may proceed through a highlyregioselective cleavage of a carbon-carbon single bond in the cyclopropane ring triggered by regioselective halometalation of the C=C bond and beta-decarbopalladation, halogen anion attack on the nonsubstituted carbon atom of the cyclopropane ring, or