2‐Azido‐2‐deoxycellulose: Synthesis and 1,3‐Dipolar Cycloaddition |
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Authors: | Fuyi Zhang Bruno Bernet Véronique Bonnet Olivier Dangles Francisco Sarabia Andrea Vasella |
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Institution: | Laboratory of Organic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Wolfgang‐Pauli‐Strasse 10, CH‐8093 Zürich |
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Abstract: | Chitosan ( 1 ) was prepared by basic hydrolysis of chitin of an average molecular weight of 70000 Da, 1H‐NMR spectra indicating almost complete deacetylation. N‐Phthaloylation of 1 yielded the known N‐phthaloylchitosan ( 2 ), which was tritylated to provide 3a and methoxytritylated to 3b . Dephthaloylation of 3a with NH2NH2?H2O gave the 6‐O‐tritylated chitosan 4a . Similarly, 3b gave the 6‐O‐methoxytritylated 4b . CuSO4‐Catalyzed diazo transfer to 4a yielded 95% of the azide 5a , and uncatalyzed diazo transfer to 4b gave 82% of azide 5b . Further treatment of 5a with CuSO4 produced 2‐azido‐2‐deoxycellulose ( 7 ). Demethoxytritylation of 5b in HCOOH gave 2‐azido‐2‐deoxy‐3,6‐di‐O‐formylcellulose ( 6 ), which was deformylated to 7 . The 1,3‐dipolar cycloaddition of 7 to a range of phenyl‐, (phenyl)alkyl‐, and alkyl‐monosubstituted alkynes in DMSO in the presence of CuI gave the 1,2,3‐triazoles 8 – 15 in high yields. |
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Keywords: | Cellulose 2‐azido‐2‐deoxy‐ Chitosan Cycloadditions ‘ Click chemistry’ 1 2 3‐Triazoles Diazo transfer |
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