WHAT DO WE COOK
Syntheses of Alkaloids Accomplished Till Date
Annulative-π-Extension (APEX):
​
Bottom-up synthesis of polycyclic aromatic hydrocarbons (PAHs) represents a cornerstone of modern nanocarbon chemistry for precise edge topology and for fine tuning optoelectronic properties. Among different regions present at the edge of arene templates, annulative-π-extension (APEX) at the bay-region is particularly challenging due to scarce functionalized precursors, with Diels-Alder cycloaddition as the sole prior method. We addressed this problem by developing ketone-directed APEX reaction at the masked bay-region by involving C–H bond functionalization employing various arene derived ketones as templets and internal alkynes. The reactions were executed by employing Rh, Co and Ru-based catalysts providing direct access to a range of exotic PAHs. Mechanistically this reaction proceeds through four distinct steps, showed excellent regioselectivity.
Allylation Chemistry:
​
Allylboronic acids hold tremendous significance as allylating agents both in terms of their reactivity and selectivity toward a number of functional groups. Although less-stable towards air, they exhibit superior nucleophilicity as well as selectivity compared to their boronate, stannane, or other metal analogues. Moreover, their ready accessibility in a geometrically pure form from the corresponding stereo-defined allyl alcohols renders them an invaluable ingredient for the total synthesis of natural products. Herein, we have demonstrated the utilization of these allylboronic acids in several asymmetric allylation reactions, and also for C2-reversed-allylation of indoles leading to the total syntheses of alkaloids. Asymmetric syntheses of a number of non-proteinogenic α-amino acids, and allylation of peptides, α-imino tertiary alcohols and α-amino ketones, α-amino imines as well as β-allylated keto imines were accomplished in high yields and diastereoselectivities. These developed methods are applicable to the total synthesis of considerable numbers of alkaloids.
Organocatalysis:
The field ‘organo-catalysis’ has thrived over three decades by working on the foundation build by the development of novel catalysts based on functionalized small organic molecules. Our research focuses on designing novel organo-catalysts. One such recent advancement from our group is development of nucleophilic catalyst based on the famous α–effect by employing readily available hydroxylamine and hydrazide in the active site of the catalysts for the electrophilic halo-functionalization. We also introduced benzoperylenocarbazole as efficient reducing organo-photoredox catalyst for various reductive transformations. In addition, utilization of visible light enables single electron transfer to the aryl halides by employing strong photoreducing naphthocarbazole based photocatalyst to form C-B, C-P, C-C bond formation along with C-N bond cleavage.
Computational Studies:
​
Our research aims to understand reaction mechanisms, regioselectivity, conformational preferences, and electron distribution in molecules through density functional theory (DFT) calculations. These studies provide the foundation for designing stereoselective reactions and for interpreting the roles of steric and electronic effects in chemical reactivity. In addition, computational insights into molecular energy levels guide the design and synthesis of polycyclic aromatic hydrocarbons (PAHs) for applications in organophotoredox catalysis and organic semiconducting materials.
