One-Pot Desulfonylative Alkylation of N-Sulfonyl Azacycles Using Alkoxides Generated by Phase-Transfer Catalysis

 

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Abstract

Sulfonamide heterocycles, specifically 3-acylindoles, undergo a deprotection/alkylation sequence in the presence of an appropriate alcohol when cesium carbonate or potassium carbonate and a phase-transfer catalyst are utilized. The outcome of the one-pot protocol was found to be significantly dependent on both the alcohol and sulfonamide heterocycle employed. Strictly anhydrous conditions are not necessary for this protocol.

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See the experimental section for preparation of this compound and related N-sulfonyl heterocycles.

N,N-Dimethylformamide was chosen as the solvent for its ability to increase the solubility of the base (K₂CO₃) and for its high boiling point.

In principle, it is harder to alkylate with a pentyl sulfonate intermediate compared to a methyl sulfonate intermediate.

The N-2 alkylated benzotriazole was clearly observed in the ^¹H NMR spectrum of the crude material, but upon purification the compound rapidly decomposed.