• Instead of the unstable formic anhydride, formylations may be carried out with formic acid and acetic anhydride to generate the mixed acetic formic anhydride in situ. For a review, see: Tetrahedron, 46, 1081 (1990). This reagent has been used for the deoxygenation of tertiary amine oxides: Chem. Lett., 1517 (1985).
• Dehydration with sulfuric acid can be used to generate CO in situ. Subsequent reaction with tertiary carbocations gives the corresponding carboxylic acid (the Koch-Haaf carboxylation). For examples, see: Org. Synth. Coll., 5, 20, 739 (1973); improved procedure: Synth. Commun., 19, 1945 (1989). 1,4-Diols in which one alcohol is tertiary give -lactones: Chem. Lett., 1187 (1982).
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In combination with Selenium(IV) oxide, 12358, improved results have been obtained in the allylic oxidation of sterically-hindered olefins: Synth. Commun., 24, 29213 (1994).• Cleaves trityl groups selectively in the presence of benzylidene acetals or TBDMS ethers: Tetrahedron Lett., 27, 579 (1986).
• Used in combination with formaldehyde in the Eschweiler-Clarke reductive methylation of amines, the formic acid acting as a hydride donor. Review: Org. React., 5, 290 (1949). For an example, see: Org. Synth. Coll., 3, 723 (1955).
• In the presence of Raney nickel alloy, reduces aromatic nitriles to aldehydes in high yield: J. Chem. Soc., 5775 (1965); for list of examples, see: Org. Synth. Coll., 6, 631 (1988).
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Hydrogen donor, in combination with Pd on carbon, in catalytic transfer hydrogenations; see, e.g.: Selective reduction of dinitroarenes to nitroanilines: J. Org. Chem., 45, 4992 (1980). Dehalogenation of aryl halides: Synthesis, 876 (1982). Hydrogenation of aromatic rings: Tetrahedron Lett., 33, 7477 (1992). See also Palladium, A12012, Cyclohexene, A11359, and Ammonium formate, A10699. For a comparative mechanistic study of formic acid and formate salts in hydrogenolysis of aryl chlorides, see: J. Org. Chem., 60, 1347 (1995).
Corrosive (C)
Irritant (Xi)
