N-Sulphonyl Pyridinium Salts in the Hetarylation Reaction

Synthesis and Characterization of a Carbene·SO2 Adduct − New Insights into the Structure and Bonding of Thiourea S,S‐Dioxides

“…The structural and spectroscopic data characterize 7 as a Lewis acid‐base adduct of the carbene 6 and are inconsistent with those presented for 5′ which has been described as a stable sulfene (short C‐S bond, planar N 2 CSO 2 framework) 9b. This discrepancy and the doubts raised about the existence of 5′ elsewhere,10b,10c have prompted us to study the bonding situation through high level quantum chemical methods 18−22…”

“…Reaction of the stable carbene 3 or 3′ with SO 2 did not give any indication of the formation of 5 (previously unknown) or 5′ (ref 9b…”

“…In 1994, Skrypnik and Lyashchuk reported the isolation of the diamino ketene 4′ 9a,9c and the stable sulfene 5′ (Scheme ) 9b,9c. The existence of 4′ has since been refuted through high level ab initio calculations10 which demonstrated that 4′ would only have the marginal stability of a van‐der‐Waals complex 10.…”

“…Two notes questioning the existence of 5′ 10b,10c have appeared in the literature, but, in the absence of additional experimental or computational data, the issue remains unresolved. X‐ray data reported for 5′ 9b are limited to selected bond lengths and bond angles and have not been deposited in the Cambridge database.…”

N‐Heterocyclic Olefin–Carbon Dioxide and –Sulfur Dioxide Adducts: Structures and Interesting Reactivity Patterns

“…Accordingt ol iterature reports, aromatic NHCs such as 16 do not form stable adducts with SO 2 . [35] Previous reports of an adamantyl-substituted aromatic NHC-SO 2 adduct in the form of ap lanar sulfene [36] have been doubted. [37] Our experiments showed,h owever,t hat NHO 7 as well as NHC 16 react selectively with SO 2 to form stable adducts.…”