Strain‐Promoted 1,3‐Dithiolium‐4‐olates–Alkyne Cycloaddition

Abstract

Reported here is the reactivity of mesoionic 1,3‐dithiolium‐4‐olates towards strained alkynes, leading to thiophene cycloaddition products. In the process, the potential of these dipoles towards orthogonal reaction with azides, allowing efficient double ligation reactions, was discovered. A versatile process to access benzo[c]thiophenes, in an unprecedented divergent fashion, was developed and provides a new entry to unconventional polyaromatic thiophenes.

o-Silylaryl Triflates: A Journey of Kobayashi Aryne Precursors

“…Recently, Audisio, Taran, and co-workers prepared a series of 1,3-dithiolium-4-olates (DTOs) 4-122 and studied their reactivity with strained alkynes. 319 As shown in Scheme 41a, various benzo[c]thiophenes 4-124 were facilely prepared through an aryne [3 + 2] cycloaddition/extrusion of carbonyl sulfide (COS) sequence via intermediate 4-123. Another type of cyclic 1,3-dipole is thiadiazole.…”

Mechanisms and Substituent Effects of Metal-Free Bioorthogonal Reactions

“…It is speculated that such a bond could be sensitive to reductive scission under physiological conditions leading to opening of the heterocyclic ring . Nonetheless, nitrones and nitrile oxides have been employed for the labeling of biomolecules and efforts to employ dipoles other than azides in a bioorthogonal context continue to be pursued …”

“…275 Nonetheless, nitrones and nitrile oxides have been employed for the labeling of biomolecules and efforts to employ dipoles other than azides in a bioorthogonal context continue to be pursued. 276 4.4.4. Nitrile Imines.…”

Design and Development of a Bioorthogonal, Visualizable and Mitochondria‐Targeted Hydrogen Sulfide (H2S) Delivery System

“…In 2019, Taran, Audisio, and co‐workers reported a strain‐promoted cycloaddition reaction between 1,3‐dithiolium‐4‐olates (DTOs) and cyclooctyne or benzyne derivatives [20] . The reaction occurs through a [3+2] cycloaddition to form a bridged intermediate, which then undergoes a retro‐Diels–Alder reaction to afford the thiophene or benzo[c]thiophene cycloadduct and COS as byproduct.…”