Synthesis of gem-Dimethylcyclopentane-Fused Arenes with Various Topologies via TBD-Mediated Dehydro-Diels–Alder Reaction

Abstract

The development of efficient methods for the synthesis of substituted polycyclic arenes with various topologies is in high demand due to their excellent electrical and optical properties. In this work, a series of gem-dimethylcyclopentane-fused arenes with more than ten topologies were synthesized via a 1,5,7-Triazabicyclo[4.4.0]­dec-5-ene (TBD)-mediated dehydro-Diels–Alder reaction with moderate to good yields. The introduction of the near-planar gem-dimethylcyclopentane moiety not only impacts the molecular conjugative system but also regulates the intermolecular π–π interactions and crystal packing, which are critical for the photoelectric performance of arenes. The photophysical properties, molecular geometry, molecular packing of these compounds, and electrochemical properties were investigated by UV–vis absorption, fluorescence emission spectra, DFT calculations, single-crystal X-ray structure analysis, and cyclic voltammetry study.

In Situ Allene Formation via Alkyne Tautomerization to Promote [4 + 2]-Cycloadditions with a Pendant Alkyne or Nitrile

“…density functional theory (DFT) results in Figure discussed as follows), the steric demands are minimal. In a second example, the double cyclization of the furan-containing precursor 19 afforded the dipyridofuran 20 in excellent yield at room temperature (Figure b) . These reactions demonstrate the facile synthesis of compounds having a structural motif that could serve as bidentate ligands.…”

Sequential Strategies to Trigger Mild Dearomative Diels–Alder Cyclizations

“…Several dearomative Diels–Alder methods have been reported in the literature to assemble functional , and bioactive molecules, , using either a thermal , or a catalytic approach. , In all cases, relatively harsh conditions (>150 °C) and/or strongly polarized substrates , are required. The product often has an aromatized naphthyl unit, and the isolation of the dihydronaphthalene derivative is rare (Scheme ).…”

“…The sequence leading to 5 is the first example of a dearomative Diels–Alder cyclization using electronically unbiased partners. − ,− ,, Applications are at present limited to the use of extended aromatics, for which the intermediate dearomatization has a lower energetic cost compared to that of phenyl groups (such as those of enynes 1 ) because of the energy mismatch in the frontier orbitals involved in the cycloaddition.…”

“…Polarized substrates are required in dearomative Diels–Alder cyclization. − ,− , We speculate that the donating ability of the carbonyl oxygen of the propiolate arm is crucial to ensure lithium coordination ( I ) , because no annulation occurred on ynones under identical conditions . The coordination polarizes the alkyne, paving the way for the dearomative Diels–Alder reaction.…”