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The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. [1] [2] In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step.
The Wharton olefin synthesis or the Wharton reaction is a chemical reaction that involves the reduction of α,β-epoxy ketones using hydrazine to give allylic alcohols. [1] [2] [3] This reaction, introduced in 1961 by P. S. Wharton, is an extension of the Wolff–Kishner reduction.
Due to its simplicity, shortened reaction times, and generally good yield, Huang's modification was a useful enough improvement that it came to displace the original procedure developed for the Wolff-Kishner reaction, and his conditions are often the ones that appear in introductory textbooks.
Mechanism of Wolff-Kishner reduction. Aromatic carbonyls are more readily reduced to their respective alkanes than aliphatic compounds. [26] For example, ketones are reduced to their respective alkyl benzenes by catalytic hydrogenation [27] [28] or by Birch reduction [29] under mild conditions.
In 1910 he described the catalytic decomposition of alcylidenhydrazines, which was later named as the Wolff–Kishner reduction. [1] [3] [4] In 1912, Kischner later applied the catalytic decomposition to pyrazoline bases and developed a versatile method for the preparation of substituted cyclopropanes by thermal decomposition of pyrazolines.
The 4-acetyl group could easily be converted to a 4-ethyl group by Wolff-Kishner reduction (hydrazine and alkali, heated); hydrogenolysis, or the use of diborane. Benzyl or tert-butyl acetoacetates also work well in this system, and with close temperature control, the tert-butyl system gives a very high yield (close to 80%). [10]
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The reaction is occasionally called the Wolff-Schröter rearrangement. [2] The Wolff rearrangement was not commonly used until 20 years after it was discovered, as facile diazo ketone synthesis was unknown until the 1930s. [2] The reaction has proven useful in synthetic organic chemistry and many reviews have been published. [1] [2] Wolff's ...