A novel visible-light-promoted coupling of diazoketones with sulfoxonium ylides, employing a violet light-emitting diode, is described under both batch and continuous flow conditions. This transformation permits the direct synthesis of synthetically useful 1,3-dicarbonyl sulfoxonium ylides (33 examples, 21-85% yields), by means of an acylation from the in situ and selective generation of ketenes. The reaction performed under flow conditions proved to be very efficient, providing the 1,3-dicarbonyl sulfoxonium ylides with higher yields and shorter reaction times.