title: Lewis Acid-Promoted Reactions of 3-Methoxy-N-(benzenesulfonyl)-1,4-benzoquinone Monoimine with Propenylbenzenes.
abstract: BF(3).OEt(2)-promoted reactions of 4-N-(benzenesulfonyl)-3-methoxy-1,4-benzoquinone monoimine (5) with (E)-propenylbenzenes bearing strong electron-donating groups on their aromaric rings produce 2-aryl-6-methoxy-3-methyl-5-[N-(benzenesulfonyl)amino]-2,3-diydrobenzofurans (6). With neutral propenylbenzenes, either the dihydrobenzofurans, bicyclo[3.2.1]octenediones 17, or products of tandem cycloaddition (7-9) are formed depending upon reaction conditions. In the latter, molecules with seven to eight asymmetric centers are formed in a single reaction from achiral starting materials. Thus, these seemingly simple reactions yield products of remarkable complexity, and with a high degree of stereoselectivity.
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, Kansas 66045.
authors.forename: Thomas A.
authors.initials: TA
authors.lastname: Engler
authors.forename: Cynthia M.
authors.initials: CM
authors.lastname: Scheibe