One-Pot Reductive Acetylation of Aldehydes using 1-Hydrosilatrane in Acetic Acid

Abstract

A one-pot, direct reductive acetylation of aldehydes was achieved under mild conditions using 1-hydrosilatrane as a safe and easily accessible catalyst. Described herein is a facile synthesis that produces acylated primary alcohols that can serve as valuable building blocks for organic synthesis. The method has good functional group tolerance and works for a range of aryl aldehydes, with the notable exception of electron-rich arenes. A library of esters was isolated by flash chromatography in yields as high as 92%.

Key words

esterification - reduction - silatrane - one-pot synthesis

• References

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• 24 General Experimental Procedure: A 25-mL round-bottom flask was charged with a magnetic stirrer bar, 1-hydrosilatrane (10 mmol), and the aldehyde starting reagent (5 mmol) dissolved in acetic acid (5 mL). The flask was capped with a water-cooled reflux condenser and heated to reflux in a silicon oil bath for 24 hours at 120 °C. Following cooling of the mixture to room temperature, the resulting gel/solid was then crushed and suspended or dissolved in 1 M aqueous HCl (ca. 20 mL) before being transferred to a 125 mL separatory funnel. The aqueous mixture was extracted three times with dichloromethane (30–50 mL) and the combined organic extracts were dried over anhydrous sodium sulfate. The solution was then filtered and concentrated under reduced pressure. The crude product was purified by column chromatography using various hexane/ethyl acetate mixtures to afford the purified product
• 25 Characterization data for benzyl acetate (3a): Yield: 64% (3.2 mmol). ¹H NMR (300 MHz, CDCl₃): δ = 7.42–7.29 (m, 5 H), 5.14 (s, 2 H), 2.13 (s, 3 H). ¹³C NMR (75 MHz, CDCl₃): δ = 170.9, 136.0, 128.6, 128.2, 66.3, 21.0. IR (ATR): 1738, 1223, 1026, 737, 696 cm^–1
• 26 Characterization data for naphthalen-1-ylmethyl acetate (3o): Yield: 71% (3.55 mmol). ¹H NMR (300 MHz, CDCl₃): δ = 8.039 (d, J = 8.1 Hz, 1 H), 7.93–7.87 (m, 2 H), 7.62–7.45 (m, 4 H), 5.60 (s, 1 H), 2.14 (s, 3 H). ¹³C NMR (75 MHz, CDCl₃): δ = 171.0, 133.7, 131.6, 131.5, 129.3, 128.7, 127.5, 126.6, 126.0, 125.3, 123.5, 64.6, 21.0. IR (ATR): 1736, 1221, 1022, 793, 773 cm^–1