Furo[3,2-b]pyrrole-5-carboxylate as a Rich Source of Fused Heterocycles: Study of Synthesis, Reactions, Biological Activity and Applications

Furo[3,2-b]pyrroles (FPs) are important members of the heteropentalene family. In particular, furo[3,2-b]pyrrole-5-carboxylates (FPcs) are commonly used as versatile building blocks for the synthesis of a large library of FP derivatives. Their structure with five potential reaction centres and an electron-rich character enables a wide range of transformations, from simple substitutions to multi-step reactions, yielding complex compounds with a furo[3,2-b]pyrrole scaffold. Many furo[3,2-b]pyrrole derivatives exhibit promising biological activity, while others have been employed in the construction of π-conjugated fused systems for optoelectronics. Efficient synthetic routes to furo[3,2-b]pyrrole derivatives are therefore of considerable interest. This review focuses on the synthetic methods leading to furo[3,2-b]pyrrole-5-carboxylates (FPcs), from the first successful attempts in the 1970s to recent approaches. Various methodologies are reported for the construction of complex molecules built from furo[3,2-b]pyrrole-5-carboxylates, emphasising their utility in the synthesis of fused heterocycles. This review also covers recent advances in screening for biological activity and applications such as fluorescent dyes.