Yb(OTf)3-catalyzed reactions of 5-alkylidene Meldrum's acids with phenols: one-pot assembly of 3,4-dihydrocoumarins, 4-chromanones, coumarins, and chromones.
[reaction: see text] The Yb(OTf)3-catalyzed annulation reactions of phenols with 5-alkylidene Meldrum's acids enabled the synthesis of structurally diverse heterocycles in high isolated yields. A series of 4-substituted 3,4-dihydrocoumarins, 2,2-disubstituted 4-chromanones, coumarins, and 2-substituted chromones were readily and efficiently assembled, including the naturally occurring coumarins citropten, scoparone, and ayapin. Addition of phenols to biselectrophilic 5-alkylidene Meldrum's acids proceeded through two distinct multibond-forming modes: Friedel-Crafts C-alkylation/O-acylation and Friedel-Crafts C-acylation/O-alkylation. The regioselectivity of the catalytic annulation reaction was controlled by the degree of substitution on the alkylidene moiety.
Fillion
Eric
E
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada. efillion@uwaterloo.ca
Dumas
Aaron M
AM
Kuropatwa
Bryan A
BA
Malhotra
Neil R
NR
Sitler
Tamsyn C
TC
D000143:Acids / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry*; D002384:Catalysis; D002867:Chromones / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D015018:Ytterbium / Q000737:chemistry*
D000143:Acids; D000475:Alkenes; D000880:Anthraquinones; D002867:Chromones; D003374:Coumarins; D009942:Organometallic Compounds; D010636:Phenols; C469373:chaetomanone; D006859:Hydrogen; C030123:coumarin; D015018:Ytterbium