ChemInform Abstract: Catalytic Reduction of Pyridinium, Pyrylium, and Thiopyrylium Salts

Abstract

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Heterocyclic Group Transfer Reactions with I(III) N-HVI Reagents: Access to N-Alkyl (Heteroaryl)onium Salts via Olefin Aminolactonization

“…In organic chemistry, they serve as ionic liquids 5 (2) and phase transfer catalysts 6 , exhibit a diverse range of biological activities (3,4) (Figure 1a), and have a long history as synthetic intermediates, an area that has seen a recent surge of new advancements. Representative of their versatile reactivity, pyridinium and related salts can undergo full or partial reductions [7][8][9] , cycloadditions 10,11 , photochemical isomerizations 12 , cross couplings 13 , addition of one-or two-electron heteroatom or carbon nucleophiles 8,14 , and facile C-H metalations 15 , and many of these include asymmetric variants [16][17][18] (Figure 1b). The breadth of available transformations make pyridinium salts valuable templates for accessing functionalized 6-membered aza-heterocyclic scaffolds, which are prevalent in agrochemicals, alkaloid natural products, and are the most commonly encountered heterocyclic motif in FDA approved small molecule drugs 19 .…”

Heterocyclic Group Transfer Reactions with I(III) N-HVI Reagents: Access to N-Alkyl (Heteroaryl)onium Salts via Olefin Aminolactonization

“…In organic chemistry, they serve as ionic liquids 5 (2) and phase transfer catalysts 6 , exhibit a diverse range of biological activities (3, 4) (Figure 1a), and have a long history as synthetic intermediates, an area that has seen a recent surge of new advancements. Representative of their versatile reactivity, pyridinium and related salts can undergo full or partial reductions [7][8][9] , cycloadditions 10,11 , photochemical isomerizations 12 , cross couplings 13 , addition of one-or two-electron heteroatom or carbon nucleophiles 8,14 , and facile C-H metalations 15 , and many of these include asymmetric variants [16][17][18] (Figure 1b). The breadth of available transformations make pyridinium salts valuable templates for accessing functionalized 6-membered aza-heterocyclic scaffolds, which are prevalent in agrochemicals, alkaloid natural products, and are the most commonly encountered heterocyclic motif in FDA approved small molecule drugs 19 .…”

“…N-HVIs possess two datively bound heterocyclic nitrogen ligands on the central iodine, resulting in altered and often novel reactivity relative to their common ArIX2 counterparts. N-HVIs can be isolated as bench stable white solids upon treatment of commercially available PhI(OAc)2 (7) with a silyl triflate activator and the Nheterocycle of choice, making modular incorporation of diverse heterocyclic motifs very straightforward.…”