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Molecules 2013, 18(12), 15613-15623; doi:10.3390/molecules181215613
Article

Total Synthesis of Six 3,4-Unsubstituted Coumarins

1
, 1,2,* , 1
, 1
 and 1
1 Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin 150040, China 2 College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, China
* Author to whom correspondence should be addressed.
Received: 28 October 2013 / Revised: 8 December 2013 / Accepted: 10 December 2013 / Published: 13 December 2013
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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.
Keywords: 3,4-unsubstituted coumarins; o-hydroxybenzaldehyde derivatives; 6,7,8-trimethoxycoumarin; 7-hydroxy-6-ethoxycoumarin 3,4-unsubstituted coumarins; o-hydroxybenzaldehyde derivatives; 6,7,8-trimethoxycoumarin; 7-hydroxy-6-ethoxycoumarin
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Gao, W.; Li, Q.; Chen, J.; Wang, Z.; Hua, C. Total Synthesis of Six 3,4-Unsubstituted Coumarins. Molecules 2013, 18, 15613-15623.

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