In organic synthesis, the Casiraghi formylation is the formation of a salicylaldehyde from a phenol and paraformaldehyde. The reaction requires a strong Brønsted base and a weak Lewis acid, and gives a methanol coproduct:
(H2CO)2n + nB + nLA + nHArOH → nHC(=O)ArOH + n[HB][LA:OMe] Formally, it combines the Cannizzaro disproportionation with a directed Friedel-Crafts acylation. In Casiraghi's original 1978 formulation, Grignard reagents served as both the hindered base and Lewis acid. When using MgCl2 with a nitrogen base, such as triethylamine, the reaction is also known as Casnati-Skattebøl formylation Applications include the synthesis of tocopherol derivatives.
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