BackgroundStructurally diverse aldehydes are successfully converted into acylals (1,1-diacetates) with acetic anhydride using NaHSO4-SiO2 as a mild, convenient and inexpensive catalyst under solvent-free conditions. The noteworthy features of the present system are shorter reaction times, and mild and solvent-free conditions. Furthermore, it offers chemoselective protection of aldehydes.ResultsBoth aromatic and aliphatic aldehydes reacts smoothly with acetic anhydride in presence of silica supported sodium hydrogen sulphate to afford the corresponding 1,1-diacetates in good to excellent yields. We studied competitive reactions for the acylation of aldehydes in the presence of ketones using silica supported sodium hydrogen sulphate as a catalyst. Using this catalytic system, the highly selective conversion of an aldehyde in the presence of ketone was observed.ConclusionsNaHSO4-SiO2 is a chemoselective and highly efficient catalyst for acylal formation from aldehydes. The advantages of this methodology over the reported methods is the availability of the starting materials, simplicity of acylation procedure, a clean work-up, a short reaction time, high yields and reusability.

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An efficient catalyst‐free one‐pot three‐component synthesis of penta‐substituted pyrroles has been successfully developed. A variety of penta‐substituted pyrroles were straightforwardly synthesized from good to excellent yields (78%–93%) by using easily accessible starting materials under mild conditions. This protocol also provided α‐amino ketones in good yields (87%–98%) without column chromatography.

An efficient synthetic protocol is presented for accessing 1,4-benzoxazine derivatives from 2-amino phenol derivatives via o-benzoquinones. The key step involves the Diels-Alder reaction between highly reactive o-quinone monoiminewith butyl vinyl ether/thioether to generate various benzoquinone derivatives.