A Preferred Disrotatory 4n Electron Möbius Aromatic Transition State for a Thermal Electrocyclic Reaction

Abstract

Nicht verboten: Thermische 4n‐Elektronen‐Elektrocyclisierungen von Hückel‐Strukturen verlaufen über „erlaubte“ konrotatorische Pfade. Bei einer Möbius‐Topologie können dagegen die Woodward‐Hoffmann‐Regeln außer Kraft treten, sodass ein „verbotener“ disrotatorischer Pfad bevorzugt wird – dies zeigen theoretische Studien am Dodecahexaen 1, das über eine aromatische Heilbronner‐Möbius‐Übergangsstruktur 2 in das cyclische Polyen 3 übergeht.

Demonstration of “Möbius” Aromaticity in Planar Metallacycles

“…[7f-i, [10][11][12] Since then, a considerable body of literature made the case for the role of orbital topology in twisted aromatics. [11] Not much attention has been paid yet to wave-function boundary conditions in these molecules.…”

“…Very recently, we have proposed computationally the first actual Mçbius aromatic transition structure for an electrocyclic reaction. [10] Nonetheless, and despite these intriguing developments, [11] the sole current application of Heilbronner Mçbius aromaticity is still in progress towards understanding certain conformational changes in annulenes. [12] Abstract: Mçbius aromaticity, predicted by Edgar Heilbronner in 1964, is a stabilizing effect exhibited by 4 n electron fully conjugated cyclic molecules (or transition states) with an odd number of orbital phase inversions.…”

Aromaticity‐promoted CO2 Capture by P/N‐Based Frustrated Lewis Pairs: A Theoretical Study

“…For instance, Houk and co‐workers utilized the concept of hyperconjugative aromaticity in Diels–Alder cycloadditions . Tsogoeva, and Mauksch reported a construction of Heilbronner‐Möbius aromatic conrotatory transition state (TS) in 4 n π system . Wegner and co‐workers described that bidentate borohydride Li 2 [1,2‐C 6 H 4 (BH 3 ) 2 ] can reduce CO 2 to either methanol or methane.…”

Reversal of Orbital Symmetry Control in Electrocyclic Ring Closures through Craig‐Möbius Aromaticity

“…Recently, it was recognized that proper consideration of Möbius topology in electrocyclic processes leads to products with stereoselectivity opposite to Woodward–Hoffmann rule predictions . Hence, we wondered: could a Möbius orbital array have similar and direct effects on orbital symmetry control in organometallic reactions?…”

“…Conversely, Heilbronner‐Möbius aromaticity in Möbius twisted molecules, with continuous overlap of adjacent p ‐orbitals (i.e. reminescent of a paper Möbius strip representation), has lately been extended to transition states for valence shifts and electrocyclic processes …”