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Yang, Qing‐Qing; Xiao, Wen‐Jing
European journal of organic chemistry, January 10, 2017, Volume: 2017, Issue: 2Journal Article
The first example of a catalytic asymmetric formal 4+1 annulation reaction between sulfur ylides and in situ generated ortho‐quinone methides (o‐QMs) is reported in this work. A C2‐symmetric chiral urea was identified to be the best H‐bonding catalyst, affording a wide range of chiral 2,3‐dihydrobenzofurans in high yields and moderate enantioselectivities 70–98 % yields, up to 89:11 e.r. (enantiomeric ratio). The title H‐bonding catalytic asymmetric 4+1 annulations of sulfur ylides with in situ generated ortho‐quinone methides (o‐QMs) enable the synthesis of chiral 2,3‐dihydrobenzofurans in good yields and moderate enantioselectivities.
