Tautomeric selectivity towards colchicinoids in the tosylation of colchiceine on a heterogeneous, easily removable catalyst

摘要

Here is presented an easy, rapid new method of tosylation of compounds containing acidic OH groups, such as tropolones and phenols, on a solid, removable catalyst, Amberlite IRA-400(OH); of special value is the preferential selectivity for the colchiceine tautomer la, leading to 10-tosyloxycolchicide (2)―the precursor of a variety of bioactive colchicinoids―which inverts the result of previous tosylation methodologies leading preferentially to useless 9-tosyloxyisocolchicide (3).