Aluminium Chloride Hexahydrate (AlCl₃ · 6H₂O): An Efficient, Facile, Mild, And Highly Chemoselective Catalytic Deprotection of Tert-Butyldimethylsilyl (TBS) Ethers

Abstract

tert-Butyldimethylsilyl (TBS) phenyl / alkyl ethers were cleaved to the corresponding efficiently parent hydroxyl compounds in good yields using catalytic amounts of AlCl₃ · 6H₂O by conventional or microwave-assisted heating in methanol or isopropanol solution. Intramolecular and competitive experiments demonstrated the chemoselective deprotection of TBS ethers in the presence of triisopropylsilyl and tert-butyldiphenylsilyl ethers.

GRAPHICAL ABSTRACT

Keywords:

• Alcohols
• aluminium chloride
• deprotection
• hexahydrate
• protective groups
• silyl ethers

ACKNOWLEDGMENTS

The authors thank the referee and Joseph M. Muchowski (visiting professor, UNAM) for valuable comments and suggestions, and M. N. Zavala-Segovia, L. Triana-Cruz (CCIQS UAEMéx–UNAM), and E. Díaz-Torres (UNAM) for technical support.

Notes

^a Yields refer to chromatographically pure isolated compounds.

^b In some cases no reaction occurred (NR) or product yields were very poor and ca. 80–98% of starting material was recovered.

^a Confirmed by comparison with MS, ¹H NMR, and ¹³C NMR with authentic samples.

^b Yields refer to chromatographically pure isolated compounds.

^c In some cases no reaction occurred (NR) or product yields were very poor and ca. 80–98% of starting material was recovered.

^d 100 °C, 15min.

^e 50 °C, 12h.

^a Confirmed by comparison with ¹H NMR and ¹³C NMR with authentic sample.

^b Yields refer to chromatographically pure isolated compounds.

^c 100 °C, 15min.

^d 50 °C, 12h.

^e Clearly the use of methanol is not possible in these cases.

^a Confirmed by comparison with ¹H NMR and ¹³C NMR with authentic samples.

^b Yields refer to chromatographically pure isolated compounds.

^c 50 °C, 12h.

^d 100 °C, 15min.

^e Clearly the use of isopropanol is not possible in these cases.