The present invention relates to sulfonium salts of formula (I): (I), their preparation, and utility as precursors for preparing functionalised organic compounds, wherein R1 and R2 are the same or different and each is independently selected from an optionally substituted aryl group, an optionally substituted alkynyl group, an optionally substituted alkenyl group, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, an optionally substituted cycloalkenyl group, an optionally substituted aralkyl group, an optionally substituted arylalkenyl group, an optionally substituted heteroaryl group, an optionally substituted heterocyclyl group, an optionally substituted amine, an optionally substituted alkoxy group, an optionally substituted thioether group, an optionally substituted phosphine group, an optionally substituted boron species, an optionally substituted carbene, an organometallic moiety, and a halide, or R1 and R2 are joined together to form an optionally substituted sulfur-containing ring； W is a bond, an optionally substituted alkynylene group, an optionally substituted alkenylene group, and optionally substituted alkylene group, an optionally substituted heterocyclyl group, an optionally substituted aryl group or an optionally substituted heteroaryl group； R3 is a moiety comprising at least one basic group, provided that when R3 does not contain any carbon atoms, W is not a bond； X is an anionic species； and n is an integer selected from 1 to 5.
