Science of Synthesis

Escher, I.; Glorius, F., Science of Synthesis, (2007) 25, 742.

A number of methods for the synthesis of α,β-unsaturated aldehydes proceed via protected α,β-unsaturated acetals or imine derivatives. α,β-Unsaturated acetals are cleaved readily in the presence of an acid such as formic acid,[‌45‌,‌63‌] aqueous hydrochloric acid,[‌64‌,‌65‌] or 4-toluenesulfonic acid.[‌66‌] An example of the use of hydrochloric acid is shown in ‌Scheme 12‌; here the acetal ‌16‌ is selectively deprotected to form the aldehyde ‌17‌, a precursor of the natural product pseurotin A.[‌64‌] Other mild and efficient metal-catalyzed processes have been reported.[‌67‌–‌70‌] Deprotection under neutral conditions can be achieved using β-cyclodextrin in water.[‌71‌] α,β-Unsaturated imines are conveniently hydrolyzed with zinc(II) choride in aqueous alcohol or in the presence of silica gel.[‌72‌,‌73‌]

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References

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