NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions
Selective acylation of saccharides is an important basic transformation in saccharide chemistry. Synthetic strategies and protocols for saccharides can reach broad users when reagents are simple (inexpensive and readily available), green, and easy to handle. Herein, we disclose that the simplest bor...
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sg-ntu-dr.10356-1790252024-07-19T15:31:48Z NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions Jin, Jiamiao Guo, Jiangtao Xu, Feng Lv, Ya Wang, Guanjie Song, Jia Lv, Wen-Xin Li, Tingting Chi, Robin Yonggui School of Chemistry, Chemical Engineering and Biotechnology Chemistry Green solution Mechanistics Selective acylation of saccharides is an important basic transformation in saccharide chemistry. Synthetic strategies and protocols for saccharides can reach broad users when reagents are simple (inexpensive and readily available), green, and easy to handle. Herein, we disclose that the simplest boric acid, B(OH)3, can work as an effective promoter for C3-OH selective acylation of unprotected monosaccharides under the catalysis of a readily available N-heterocyclic carbene catalyst. Solvents such as THF from untreated commercial sources can be directly used. Mechanistically, the boric acid plays multiple roles in benefiting reaction yields and regioselectivities, including solubilizing the saccharide substrates by forming borate esters with the saccharides, shielding the C6-OH unit of the saccharides from acylation, and enhancing the selectivity between C3-OH and C2-OH reactions. We also found that the solvent has a profounder effect on the reaction yield and selectivity than the base. Selectively acylated saccharide products can be easily obtained with good-to-excellent yields and gram scales. Our study will encourage the further development of new synthetic strategies for saccharides that can reach beyond laboratory scales and to scientists not necessarily with expertise in organic synthesis. Compared to previous methods using aryl and alkyl boronic acids as modulating reagents, the use of boric acid provides a greener solution economically and environmentally. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version We acknowledge funding support from the National Key Research and Development Program of China (2022YFD1700300), the National Natural Science Foundation of China (U23A20201, 22071036), the Frontiers Science Center for Asymmetric Synthesis and Medicinal Molecules, Department of Education, Guizhou Province [Qianjiaohe KY number (2020)004], the Natural Science Foundation of Guizhou University [Guida Tegang Hezi (2023)23], the Program of Introducing Talents of Discipline to Universities of China (111 Program, D20023) at Guizhou University, the Singapore National Research Foundation under its NRF Competitive Research Program (NRF-CRP22-2019-0002), the Singapore Ministry of Education under its MOE AcRF Tier 1 Award (RG70/21, RG84/22), MOE AcRF Tier 2 Award (MOE-T2EP10222-0006), and MOE AcRF Tier 3 Award (MOE2018-T3-1-003), a Chair Professorship Grant, and Nanyang Technological University. 2024-07-16T06:43:00Z 2024-07-16T06:43:00Z 2024 Journal Article Jin, J., Guo, J., Xu, F., Lv, Y., Wang, G., Song, J., Lv, W., Li, T. & Chi, R. Y. (2024). NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions. Green Chemistry, 26(10), 5997-6004. https://dx.doi.org/10.1039/d3gc05005j 1463-9262 https://hdl.handle.net/10356/179025 10.1039/d3gc05005j 2-s2.0-85190736310 10 26 5997 6004 en NRF-CRP22-2019-0002 RG70/21 RG84/22 MOE-T2EP10222-0006 MOE2018-T3-1-003 Green Chemistry © The Author(s). This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. application/pdf |
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Chemistry Green solution Mechanistics Jin, Jiamiao Guo, Jiangtao Xu, Feng Lv, Ya Wang, Guanjie Song, Jia Lv, Wen-Xin Li, Tingting Chi, Robin Yonggui NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
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Selective acylation of saccharides is an important basic transformation in saccharide chemistry. Synthetic strategies and protocols for saccharides can reach broad users when reagents are simple (inexpensive and readily available), green, and easy to handle. Herein, we disclose that the simplest boric acid, B(OH)3, can work as an effective promoter for C3-OH selective acylation of unprotected monosaccharides under the catalysis of a readily available N-heterocyclic carbene catalyst. Solvents such as THF from untreated commercial sources can be directly used. Mechanistically, the boric acid plays multiple roles in benefiting reaction yields and regioselectivities, including solubilizing the saccharide substrates by forming borate esters with the saccharides, shielding the C6-OH unit of the saccharides from acylation, and enhancing the selectivity between C3-OH and C2-OH reactions. We also found that the solvent has a profounder effect on the reaction yield and selectivity than the base. Selectively acylated saccharide products can be easily obtained with good-to-excellent yields and gram scales. Our study will encourage the further development of new synthetic strategies for saccharides that can reach beyond laboratory scales and to scientists not necessarily with expertise in organic synthesis. Compared to previous methods using aryl and alkyl boronic acids as modulating reagents, the use of boric acid provides a greener solution economically and environmentally. |
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School of Chemistry, Chemical Engineering and Biotechnology |
author_facet |
School of Chemistry, Chemical Engineering and Biotechnology Jin, Jiamiao Guo, Jiangtao Xu, Feng Lv, Ya Wang, Guanjie Song, Jia Lv, Wen-Xin Li, Tingting Chi, Robin Yonggui |
format |
Article |
author |
Jin, Jiamiao Guo, Jiangtao Xu, Feng Lv, Ya Wang, Guanjie Song, Jia Lv, Wen-Xin Li, Tingting Chi, Robin Yonggui |
author_sort |
Jin, Jiamiao |
title |
NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
title_short |
NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
title_full |
NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
title_fullStr |
NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
title_full_unstemmed |
NHC/B(OH)3-mediated C3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
title_sort |
nhc/b(oh)3-mediated c3-selective acylation of unprotected monosaccharides: mechanistic insights and toward simpler/greener solutions |
publishDate |
2024 |
url |
https://hdl.handle.net/10356/179025 |
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1814047231331794944 |