A new, wide ranging, synthetically powerful, catalytic tandem cyclisation-anion capture process is proposed which depends on the rate of cyclisation of an organopalladium specifies (RPdX) onto a proximate alkene or diene being significantly faster than anion exchange and reductive elimination in the sequence RPdX→ RPdY→ RY+ Pd (0). The catalytic cyclisation-anion capture sequence is illustrated for hydride capture by a wide ...