In summary, we have discovered a strain-release controlled [4+2+1] reaction of CP-capped diene-ynes/diene-enes and CO catalyzed by [Rh(CO)2Cl]2. The reaction has a broad scope and various 5/7 bicyclic molecules with CP group can be synthesized. Of the same importance, the 5/7 products can be further transformed into either functionalized 5/7 molecules or multicyclic 5/7/5, 5/7/6, and 5/7/7 skeletons by using the CP group as an advanced intermediate group (CP Chem). Quantum chemical calculations have been carried out to understand the detailed steps of this [4+2+1] reaction. Especially, the role of CP to avoid the possible competing [2+2+1] reaction, has been identified, showing the strain-release of the MCP moiety in the CP-capped dienes (about 7 kcal/mol) is the key to prefer the [4+2+1] over the [2+2+1] reaction.