Serendipitous Rediscovery of the Facile Cyclization of Z,Z‐3,5‐Octadiene‐1,7‐diyne Derivatives to Afford Stable, Substituted Naphthocyclobutadienes

Abstract

The serendipitous isolation of very small amounts of two naphthocyclobutadiene (NCB) derivatives has led to the computational re‐examination of the electrocyclization of Z,Z‐3,5‐octadiene‐1,7‐diyne as well as the experimental and computational study of diethynylindeno[2,1‐a]fluorene derivatives that contain the 3,5‐octadiene‐1,7‐diyne motif as part of a larger π‐framework. In both cases the calculated potential energy surface strongly implicates two successive electrocyclic reactions to afford the antiaromatic products. With the octadienediyne fragment locked in the reactive conformation, the postulated diethynylindeno[2,1‐a]fluorene intermediates afford the NCBs in modest to good yields. X‐ray crystallography of four NCBs as well as NICS‐XY scan calculations show that the paratropic motif is located primarily in the benzocyclobutadiene fragment within the larger π‐scaffold.

Organic Semiconductors Derived from Dinaphtho-Fused s-Indacenes: How Molecular Structure and Film Morphology Influence Thin-Film Transistor Performance

“…The three TIPS DNI regioisomers along with the TIBS DNI were prepared as previously described. , The nODIPS DNI compound was synthesized in an analogous manner, the details of which are in the Supporting Information and Figure S1.…”

Copper(III) Metallacyclopentadienes via Zirconocene Transfer and Reductive Elimination to an Isolable Phenanthrocyclobutadiene

“…In these fused ring systems, the double-bond characteristic of the shared edge determines the degree of antiaromaticity (and consequently the instability) of the PAH–CBD conjugate . Thus, whereas CBDs appended to highly delocalized ring systems (e.g., benzene and naphthalene) have been isolated, − phenanthrene-fused CBDs have proven elusive due to the highly localized double bond on the central phenanthrene ring. − Access to fused ring PAH–CBDs has also been severely limited by the lack of appropriate synthetic methodologies.…”

Revisiting indeno[1,2-b]fluorene by steric promoted synthesis while isolating the second stable 4nπ indeno[2,1-a]fluorene

“…16 The presence of the o -QDM subunit makes polycyclic hydrocarbon (PH) quite unstable due to the reactive s-cis diene substructure. 17 Tobe et al demonstrated that bulky mesityl (Mes) group-protected s-cis diene containing o -QDM embedded 11,12-mesityl disubstituted [2,1- a ]IF 3 b was isolable and stable and its crystallographic characterization was possible, whereas the same [2,1- a ]IF unit with ethynyl 18 or phenyl 19,3 b substitution at the apical carbon was either difficult to isolate or was unstable. The formally antiaromatic [2,1- a ]IF was a closed-shell molecule with a large singlet–triplet energy gap (13.5 kcal mol −1 or 0.58 eV).…”