A new concept for the efficient synthesis of a chiral phosphorus-nitrogen-carbon cage-compound is reported, which is comprised of a high-yield three-step procedure starting from a P-Cp*-substituted 2H-azaphosphirene complex. Thermolysis of a solution of the latter complex in the presence of Ph 3 PNCN and DMAD afforded the P-Cp*-substituted 2H-1,2-azaphosphole complex 11 in a clean reaction; a further reaction at 75°C with DMAD produced complex 12 via an intermolecular Diels−Alder reaction of the Cp* group. A sub-