Uncovering the hidden reactivity of benzyne/aryne precursors utilized under milder condition: Bonding and stability studies by EDA‐NOCV analyses

Abstract

Arenes [C6H3R(TMS)(OTf); also called benzyne/aryne precursors] containing inter‐related leaving groups Me3Si (TMS) and CF3SO3(OTf) on the adjacent positions (1,2‐position) are generally converted to their corresponding aryne‐intermediates via the addition of fluoride anion (F−) and subsequent elimination of TMS and OTf groups. This reaction is believed to proceed via the formation of an anionic intermediate [C6H4(TMS‐F)(OTf)]−. The EDA‐NOCV analysis (EDA‐NOCV = energy decomposition analysis‐natural orbital for chemical valence) of over 35 such precursors of varied types have been reported to reveal bonding and stability of CArSi and COTf bonds. EDA‐NOCV showed that the nature of the CArSi bond of C6H3R(TMS)(OTf) can be expressed as both dative and electron sharing [CArSi, CAr→Si]. The CArOTf bond, on the other hand, can be described explicitly as dative [CAr←OTf]. The nature of CArSi bond of [C6H4(TMS‐F)(OTf)]− exclusively changes to covalent dative σ‐bond CAr→S(Me)3F on the attachment of F− to the TMS group of C6H4(TMS)(OTf). Introduction of σ‐electron withdrawing group (like OMe, NMe2, and NO2) to the ortho‐position of the TMS group of functionalized arynes C6H3R(TMS)(OTf) prefer to have a covalent dative σ‐bond (CAr→Si) over an electron‐sharing covalent σ‐bond (CArSi). If this σ‐electron withdrawing group is shifted from ortho‐position to meta‐ and para‐positions, then the preference for a dative bond decreases significantly, implying that the electronic effect on the nature of chemical bonds affects through bond paths. This effect dies with distance, similar to the well‐known inductive effect.

Catalytic Enantioselective Nucleophilic Addition to Arynes by a New Quaternary Guanidinium Salt-Based Phase-Transfer Catalyst

“…The catalytic asymmetric reactions involving arynes are significantly challenging − because of the neutral, relatively reactive short-lived nature of aryne intermediates, associating with undesired bond formation during the aryne trapping. , Currently, achieving highly enantioselective reactions with arynes is extremely rare, ,, with only two successful examples that have achieved enantiomeric excess (ee) values exceeding 80%. One such example involves the chiral palladium-catalyzed cross-cyclotrimerization of helicenyl aryne with dialkylacetylenedicarboxylate to construct triple helicenes, as reported by Tsurusaki and Kamikawa .…”