Bromination of lappaconitine and N-desacetyllappaconitine

Bromination of lappaconitine with a KBr—H2O2 mixture in 20% H2SO4, as well as with molecular Br2 in either Py, CH2Cl2, CH3COOH, or DMSO did not occur, while the initial lappaconitine was isolated from the reaction mixture. Such a bromination with molecular Br2 in solutions of strong acids (concentrated HCl, aqueous 50% H2SO4, and CF3COOH) gives monobromolappaconitine in the yields up to 80%. Bromination of N-desacetyllappaconitine both in organic solvents and in acid solutions leads to mono- and dibrominated derivatives.