title: Total synthesis of six 3,4-unsubstituted coumarins.
abstract: In this article we describe a new methodology for the total synthesis of 3,4-unsubstituted coumarins from commercially available starting materials. Six examples were prepared, including five naturally occurring coumarins--7-hydroxy-6,8-dimethoxy-coumarin (isofraxidin), 7-hydroxy-6-methoxycoumarin (scopoletin), 6,7,8-trimethoxy-coumarin, 6,7-dimethoxycoumarin (scoparone), and 7,8-dihydroxycoumarin (daphnetin) and one synthetic coumarin, 7-hydroxy-6-ethoxycoumarin. Moreover, five important o-hydroxybenzaldehyde intermediates were also obtained, namely 2,4-dihydroxy-3,5-dimethoxybenzaldehyde, 2,4-dihydroxy-5-methoxybenzaldehyde, 5-ethoxy-2,4-dihydroxy-benzaldehyde, 2-hydroxy-3,4,5-trimethoxybenzaldehyde, and 2-hydroxy-4,5-dimethoxy-benzaldehyde. The method developed herein involves just three or four steps and allows for the rapid synthesis of these important molecules in excellent yields. This is the first synthesis of 6,7,8-trimethoxycoumarin and 7-hydroxy-6-ethoxycoumarin.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Gao
authors.affiliation: Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin 150040, China. liqy@zjut.edu.cn.
authors.forename: Qingyong
authors.initials: Q
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Wang
authors.forename: Changlong
authors.initials: C
authors.lastname: Hua
mesh_terms: D020650:Combinatorial Chemistry Techniques; D003374:Coumarins / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure
chemical_list: D003374:Coumarins; C030123:coumarin