Answer
Robinson annulation, a significant carbon-carbon bond-forming reaction, enables the synthesis of complex organic molecules like cyclohexenones. This reaction involves the intramolecular condensation of a suitably substituted 2-acyl-1,4-diketone, forming a six-membered cyclic structure. Its significance lies in its ability to selectively construct various ring systems, making it a versatile tool for organic synthesis, especially in the pharmaceutical industry.