Burgess reagent

Technical Specifications

Product Description & Scientific Applications

The Burgess reagent, [methoxycarbonylsulfamoyl]triethylammonium hydroxide inner salt, is a mild dehydrating agent that removes water under mild, near-neutral conditions tolerant of acid-sensitive functionality. That mildness, and the absence of carbocation character in its key step, define its use.

Applications

• Alcohol-to-alkene dehydration (the defining use) — secondary and tertiary alcohols are dehydrated to alkenes: the alcohol is first converted to an alkyl N-carbomethoxysulfamate ester, which undergoes a first-order thermolytic Ei decomposition — a cis-stereospecific (syn) elimination. Because the transition state imposes a cis-β-hydrogen geometrical constraint and lacks α-carbon carbonium-ion character, the elimination is free of skeletal rearrangements and therefore predictable, a strategically useful step in directed synthesis. Primary alcohols give carbamates (urethanes) instead.
• Oxazoline formation (cyclodehydration) — β-hydroxy amides close to oxazolines, the ring-forming step toward the oxazole- and thiazole-containing cyclic peptides dendroamide A and balgacyclamide A. The oxazole itself is completed by a subsequent DBU-assisted oxidation that aromatises the oxazoline; cyclodehydration alone gives the oxazoline, not the oxazole.
• N-Bridged bicyclic pyridines — the same dehydrative cyclisation assembles N-bridged 5,6-bicyclic pyridines (pyrrolo-, imidazo- and triazolopyridines) under mild and neutral conditions that tolerate acid-sensitive groups.
• Oxabicyclic scaffolds — under acidic conditions, the reagent converts δ-diols to oxabicyclo[3.2.1]octan-3-ol scaffolds by dehydrative cyclisation.
• Amide-to-nitrile dehydration — dehydration of a primary amide to the corresponding nitrile, applied on manufacturing scale in the original route to the antiviral nirmatrelvir, where the reagent effects the amide-to-nitrile dehydration in dichloromethane.
• Alcohol oxidation (with DMSO) — beyond dehydration, in the presence of dimethyl sulfoxide the reagent oxidises a broad range of primary and secondary alcohols to the corresponding aldehydes and ketones by a mechanism related to the Pfitzner-Moffatt and Swern oxidations.

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