Some Mercuration Reactions of Substituted Pyrroles

Mercuration of N-unsubstituted pyrroles with mercury(II) acetate results in immediate precipitation of the N-mercurated derivative, which is insoluble in virtually all organic solvents. If the pyrrole N atom is protected (e.g. with Me, CH₂OCH₂Ph, or CO₂t-Bu) then mercuration takes place efficiently at unsubstituted pyrrole carbons. Subsequent palladium/olefin (Heck-type) reactions afford the corresponding pyrrole acrylate when, for example, the olefin is methyl acrylate; deprotection (when the N-substituent is CH₂OCH₂Ph or CO₂t-Bu) then affords the required carbon-substituted pyrrole. Attempts to deprotect the N-methylpyrroles were unsuccessful.