Lewis Acid Promoted Additions of Organotrifluoroborate Salts

Lewis Acid Promoted Additions of Organotrifluoroborate Salts 

For Petasis borono-Mannich reactions of formaldehyde, methylation of the amine reportedly occurs as a side-reaction, presumably by iminium ion reduction [19]. The hydride source under these conditions may be formic acid, as in the Eschweiler-Clarke methylation reaction. This problem was overcome by the use of potassium trifluoroborate salts and Lewis acids in toluene at 90 °C (the reaction in highly polar solvents such as acetonitrile, DMF and DM SO gives the reduction product). 

Kabalka and co-workers have shown that alkynyltrifluoroborate salts undergo coupling with secondary amines and salicylaldehydes (or formaldehyde) in an ionic liquid solvent at 80 °C [70]. The ionic liquid undoubtedly helps solubilize the trifluo- 

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