Fillion Eric, Dumas Aaron M, Kuropatwa Bryan A, Malhotra Neil R, Sitler Tamsyn C
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
J Org Chem. 2006 Jan 6;71(1):409-12. doi: 10.1021/jo052000t.
[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.
[反应：见正文] Yb(OTf)₃催化的酚与5-亚烷基丙二酸亚异丙酯的环化反应能够以高分离产率合成结构多样的杂环化合物。一系列4-取代的3,4-二氢香豆素、2,2-二取代的4-色满酮、香豆素和2-取代的色酮能够轻松且高效地组装而成，包括天然存在的香豆素类化合物柠檬苦素、滨蒿内酯和阿亚品。酚类与双亲电5-亚烷基丙二酸亚异丙酯的加成反应通过两种不同的多键形成模式进行：傅克C-烷基化/O-酰化和傅克C-酰化/O-烷基化。催化环化反应的区域选择性由亚烷基部分的取代程度控制。
