Phosphonium salts and aldehydes from the convenient, anhydrous reaction of aryl acetals and triphenylphosphine hydrobromide

Mani Ramanathan,Duen-Ren Hou

doi:10.3998/ark.5550190.0014.308

Abstract

The reactions of aryl acetals/ketals and triphenylphosphine hydrobromide gave the corresponding aldehydes/ketones and alkyl phosphonium bromides. This reaction was applied to convert acetals/ketals to the corresponding aldehydes/ketones under an anhydrous and convenient condition (50 oC, 5 min, up to 90% yield), and acid sensitive functional groups were compatible.

Highlights

Preparation and removal of acetals/ketals are often encountered in organic synthesis since the two functionalities are the primary protecting groups for aldehydes and ketones.[1]
We have found that the reaction of aryl acetals with the stable, non-hygroscopic, metal-free and commercially available salt, triphenylphosphine hydrobromide (PPh3HBr)[10], provides the corresponding aldehydes/ketones and phosphonium salts in good yields
It was interesting to observe that aryl acetals/ketals were susceptible to PPh3HBr, but in a different reaction pathway

Summary

Introduction

Preparation and removal of acetals/ketals are often encountered in organic synthesis since the two functionalities are the primary protecting groups for aldehydes and ketones.[1] The deprotection of acetals/ketals is usually achieved by acidic, aqueous hydrolysis.[1,2] such conditions may cause problems for moisture- or acid-sensitive substrates. We have found that the reaction of aryl acetals with the stable, non-hygroscopic, metal-free and commercially available salt, triphenylphosphine hydrobromide (PPh3HBr)[10], provides the corresponding aldehydes/ketones and phosphonium salts in good yields. This paper reports our work to develop this reaction as a convenient and selective anhydrous deprotection method for aryl acetals and ketals (Equation 1)

Methods

Results

Conclusion