Design of new processes that avoid the use of toxic reagents has been the focus of intense research of late. Catalysis by metals and non-metals offers diverse opportunities for the development of new organic reactions with promising range of selectivities-chemoselectivity, regioselectivity, diastereoselectivity, and enantioselectivity. Furthermore, these transformations frequently occur under mild conditions, tolerate a broad array of functional groups, and proceed with high stereoselectivity. The area of catalysis is sometimes referred to as a 'foundational pillar' of green chemistry. Catalytic reactions often reduce energy requirements and decrease separations because of increased selectivity; they are also capable of permitting the use of renewable feedstocks of less toxic reagents or minimizing the quantities of reagents needed. New catalytic organic synthesis methodologies have, thus, offered several possibilities for considerable improvement in the eco-compatibility of fine chemical production. Hence, these catalytic methodologies have emerged as powerful tools for the efficient and chemoselective synthesis of heterocyclic molecules.

An Introduction. Five-Membered N-Heterocycles. Five-Membered N-Polyheterocycles. Five-Membered Fused N-Heterocycles. Five-membered Fused Polyheterocycles. Five-Membered N,N-Heterocycles. Five-Membered N,N-polyheterocycles. Five-Membered Fused N,N-Heterocycles. Five-Membered N,N,N-Heterocycles