Asymmetric organocatalysis in the synthesis of heterocyclic scaffolds

In the past 20 years, the field of asymmetric organocatalysis provided an effective alternative to the more conventional metal and enzymatic catalysis. Certainly, several advantages can be recognized in the employment of small organic molecules as catalysts: i) various and simultaneous activation modes; ii) these catalysts are in general cheaper, readily available and easy to synthesize; iii) frequently, inert atmosphere and dry solvents are not necessary due to the high stability of the organocatalysts. Furthermore, the development of efficient methods for the asymmetric construction of complex heterocyclic frameworks is an ongoing challenge within the synthetic community. To achieve such a goal, organocatalyzed cascade reactions and sequential catalysis have been shown to be excellent candidates because of the number of steps that can occur under the same reaction conditions, thereby leading directly to high molecular complexity.1 In this presentation, the asymmetric synthesis of isochromanones, polycyclic ethers, and pyrazolone derivatives will be described, with particular attention on domino-sequential processes and mmulti-step syntheses.2