Denitrogenation of Tosylhydrazones: Synthesis of Aryl Alkyl Sulfones Catalysed by Phenalenyl Based Molecule

Kumar, Shiv (2023) Denitrogenation of Tosylhydrazones: Synthesis of Aryl Alkyl Sulfones Catalysed by Phenalenyl Based Molecule. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Shiv Kumar (18MS122)) Thesis_18MS122.pdf - Submitted Version Restricted to Repository staff only Download (5MB)

Abstract

Sulfur-containing organic molecules such as sulfones are prevalent in pharmaceuticals and agrochemicals. The usage of sulfur dioxide (SO₂) in synthesis gains immense popularity since the discovery of the SO₂ surrogate DABSO (the complex of DABCO and SO₂). However, the use of stoichiometric amount of nitrogen-based nucleophile (DABCO) restricts its applicability. Herein, we report a photoinduced catalytic process for in situ denitrogenative rearrangement of sulfonyl hydrazone to achieve aryl alkyl sulfone. The sulfonyl hydrazine undergoes base mediated fragmentation to form tosylate and a (diazomethyl)arene, which eventually undergoes photoinduced denitrogenation to form a transient carbene intermediate. We have used phenalenyl-based odd alternate hydrocarbon as an organo-photoredox catalyst, which act as a potent oxidant due to its easily accessible non-bonding molecular orbital (NBMO) to form a tosyl radical from tosylate. We performed radical trapping, EPR, and fluorescence quenching studies to elucidated the plausible mechanism. This method shows various functional group tolerances, with application in late-stage modification of various natural products with good to high yields. The protocol provides a safe and easy way for the formation of sulfone.

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