Development of transition-metalfree based pot-economy approaches to pyridines, spirobenzo[b]oxepines, pentafulvenes and related frameworks

Abstract

The main purpose of this thesis work is to develop novel metal-free poteconomy methodologies for the proficient synthesis of fascinating classes of highly functionalized pyridines, cyclopenta-fused-chromenes, cyclopenta-fused-benzothiaxepines, cylopropanes, hydroxypentafulvenes, spirobenzoxepine derivatives under very mild reaction conditions from easily available starting materials. The first chapter starts with the general introduction which explains the synthesis and application of pyridines, cyclopropanes, pentafulvenes, and functionalized spirobenzoxepine derivatives with historical background and synthetic routes reported for the construction of an aforesaid class of heterocyclic compounds via various synthetic modifications. The second chapter explains a new metal-oxidant-and solvent-free based eco-friendly MCR method for the modular synthesis of a diverse range of medicinally promising hydroxyarylated unsymmetrical pyridines in good to high chemical yields (55-85%) with an excellent regioselectivity. This domino process involves a range of N-sulfonyl ketimines as 2C1N sources, enolizable ketones and aromatic/heteroaromatic aldehydes using ammonium acetate as an ideal promoter under neat conditions in which creates new two C-C and one C-N bonds. Notably, the neutral reaction conditions are mild enough to tolerate a range of functionalities and cover a variety of substrates, thus bestowing a powerful avenue to access tri-and tetra-substituted pyridines including carbo-and heterocyclic-fused ones.