Science of Synthesis

Tidwell, T. T., Science of Synthesis, (2006) 23, 577.

Dehydrochlorination is a common method for generating monoalkylketenes such as butylketene (‌41‌), but this method usually requires reflux conditions and the ketenes are prone to dimerization (‌Scheme 12‌).[‌24‌–‌31‌] The generation of tert-butylketene by this method permits the IR absorption of the ketene at 2119 cm–1 to be observed in the mixture, but the ketene cannot be isolated.[‌30‌] Refluxing the solution leads to the isolation of the corresponding dimer in 30% yield.[‌30‌] As noted in Section ‌23.14.1.1.4.1‌, a shuttle procedure with a strong stoichiometric base and a catalytic kinetic base results in the effective formation of monoalkylketenes. Dehydrochlorination of acyl chlorides from fatty acids gives ketene dimers with long aliphatic side chains[‌24‌] that are of major commercial importance in the sizing of paper.[‌2‌,‌3‌] Hydrolysis of these β-lactone dimers provides a useful route to dialkyl ketones[‌27‌] as described in Section ‌23.14.1.1.3.1‌ (‌Scheme 11‌).[‌58‌] Because of the tendency for ketenes to dimerize during thermal dehydrochlorination of alkanoyl chlorides, this procedure is often used with in situ capture of the ketenes as they are formed.

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References

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• 8.Meeeee-Meee, (8888) 8/8, 88.
• 8.Meeeee-Meee, (8888) M 88e, 888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.