Barton reaction

The Barton reaction is one of the name reactions in organic chemistry and is named after Derek Harold Richard Barton, who first published in 1960.

Overview reaction

In the Barton reaction, a nitrite is photolytically converted to a δ -hydroxy- substituted oxime.

Because you can oximes to carbonyl compounds (R = H, R = Organylgruppe aldehyde or ketone ) hydrolyze about this reaction sequence also δ -hydroxy -substituted aldehydes or ketones are ultimately accessible.

Reaction mechanism

By the action of ultraviolet light, is divided and the nitrous acid ester, a nitric oxide radical is split off at the same time creates an alkoxy radical. The alkoxy radical abstracts a six -membered transition state, a δ - hydrogen atom, it creates a carbon radical. This recombined with the nitric oxide radical to the δ - Nitrosoalkohol from the forms by a 1,3 proton shift a δ -hydroxy- substituted oxime:

Optional sequence reaction: Hydrolysis of the oxime can be the appropriate carbonyl compound δ -hydroxy -substituted aldehyde or ketone. In this manner could Barton in the synthesis of aldosterone, the methyl group in the 18- position of the Corticosteronacetats into the required formyl (aldehyde ) converted.

Application (selection)

The obtained during the Barton reaction δ - Nitrosoalkohole are useful synthetic intermediates. In a multi-step partial synthesis of natural products used T. Konoike and his staff in a key step in the Barton reaction to synthesise an oxime:

Similarly, the Barton reaction is also used in the synthesis of antibiotics. Cephalosporins are important antibiotics, however, a number of pathogenic microorganisms with β - Lactameseaktivität have developed a resistance to these antibiotics. I. Chao and his colleagues therefore tried a new antibiotic - based on cephalosporins - to produce. They prepared the β -lactam 2, which is resistant to β -lactamase. An important step in the synthetic sequence was the Barton reaction. As the isomeric oximes were 1a and 1b is generated and converted to the β -lactam 2.