Silica-Gel Supported Sulfamic Acid (SA/SiO₂) as an Efficient and Reusable Catalyst for Conversion of Ketones into Oxathioacetals and Dithioacetals

Abstract

A simple and efficient method for the conversion of carbonyl compounds to oxathioacetals and dithioacetals using SA/SiO₂ as an acid catalyst has been achieved. SA/SiO₂ is easily recovered from the reaction mixture and can be reused at least 15 times without loss of catalytic activity.

GRAPHICAL ABSTRACT

Keywords:

• Acetal
• protective group
• sulfamic acid
• supported reagent

Notes

^a A mixture of 1a (2.0 mmol), 2a (2.4 mmol), and catalyst (1.5 mmol) was stirred in 1,2-dichloroethane (DCE) at room temperature for 2 h.

^b Isolated yield.

^c SA/SiO₂ was prepared by literature methods.^{[ 16 ]}

^a In all reactions 1a (2.0 mmol), 2a (2.4 mmol), SA/SiO₂ (3.0 mmol/g, 0.5 g), and solvent (5 mL) were used.

^b Yields were determined by GLC.

^a A mixture of 1a, 2a, and SA/SiO₂ was stirred in hexane at 40 °C.

^b Yields were determined by GLC.

^a Parenthetic numbers indicate the number of reuses of SA/SiO₂.

^b Isolated yield.

^a A mixture of 1a (2.0 mmol), 2a (2.4 mmol), and SA/SiO₂ (4.0 mmol/g, 0.3 g) was stirred in hexane (5 mL) at room temperature for 2 h.

^b Isolated yield.

^c Reaction was carried out using 20 mL of hexane at reflux for 1 h.

^d Reaction was carried out at reflux for 2 h.

^e Reaction was carried out at 40 °C for 12 h.

^a A mixture of 1a (2.0 mmol), 2a (2.4 mmol), and SA/SiO₂ (4.0 mmol/g, 0.3 g) was stirred in hexane (5 mL) at room temperature for 2 h.

^b Isolated yield.

^c Reaction was running for 1 h.

^d Reaction was carried out hexane (10 mL) at reflux for 1.5 h.