Expanded Radialenes with Bicyclo[4.3.1]decatriene Units: New Precursors to Cyclo[n]carbons

Abstract

A new method for the formation of conjugated polyynes has been developed based on both the rearrangement of vinylidenes to alkynes and the [2+1] cheletropic fragmentation of dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-triene derivatives. A model study of the photolysis of simple dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-trienes resulted in cheletropic fragmentation followed by 1,2-migration to give the corresponding linear polyynes, although undesired isomerization to methylenebicyclo[5.3.0]triene derivatives took place concurrently. Expanded [3]-, [4]-, [5]-, and [6]radialene derivatives with exocyclic bicyclo[4.3.1]decatriene units were prepared by oxidative coupling of the monomeric units as precursors to the corresponding cyclo[n]carbons, monocyclic forms of carbon clusters. The spectroscopic properties of the expanded radialenes were investigated in connection with cross conjugation of the core pi system and with its perturbation by the extraannular bicyclic pi system. In negative-mode laser-desorption time-of-flight (LD-TOF) mass spectra, the expanded radialenes exhibited peaks due to the corresponding cyclo[n]carbon anions (n = 18, 24, 30, and 36) formed by the stepwise loss of the aromatic indane fragments.

All‐Carbon Scaffolds by Rational Design

“…4). [26,[97][98][99][100][101] Compounds 14-16 possess persilylated C 40 (diameter excluding the silyl groups: $17 Å ), C 50 (19 Å ), and C 60 cores (22 Å ), respectively, and are high-melting (>220 8C), stable, yellow solids. [85,96] Macrocyclic cross-conjugation is not very efficient and therefore, the end-absorption of all three chromophores appears at nearly the same wavelength, below 500 nm.…”

“…Compound 20 (only one diastereoisomer is shown) is a precursor to cyclo-C 30 , and the corresponding molecular anion peak C 30 À , formed by stepwise loss of indane fragments, is observed in the negative-mode laser-desorption time-of-flight (LDÀTOF) mass spectrum. [26] The extended [9] radialene 21 forms a complex with a Ag þ ion, which most probably is incorporated in its inner cavity. The periphery of 21 contains sterically overcrowded regions and rotation of the chlorobenzene rings is slow on the NMR time scale.…”

“…[21] Since the late 1980s, elegant protocols to prepare cyclocarbons starting from defined macrocyclic dehydroannulene or expanded radialene precursors were developed but their synthesis only succeeded in the gas phase and bulk quantities have not been isolated, so far. [22][23][24][25][26] 2D carbon networks, different from graphite, as well as 3D carbon networks were proposed since the late 1980s, [23,[27][28][29] stimulated by the discovery that fullerenes are stable carbon allotropes. However, structural chemical imagination clearly exceeds current synthetic availability and hardly any of the proposed networks have become the target of serious preparative work, with two exceptions: graphyne (2) and graphdiyne (3, Fig.…”

Advanced opto-electronics materials by fullerene and acetylene scaffolding

“…Shape-persistent, conjugated macrocycles with all-carbon skeletons are of interest to many research groups [53][54][55][56][57][58][59][60][61][62][63][64]. In our research aimed at producing large all-carbon sheets [7], we have become interested in three classes of macrocycles, perethynylated dehydroannulenes [65], perethynylated expanded radialenes [66], and perethynylated radiaannulenes [68].…”

“…In 1993, we had reported the first examples of the expanded radialenes [71] and had since then continued investigating the opto-electronic properties of these novel macrocyclic chromophores [72] (for other work, see [54,55]). In continuation of this work, three series of perethynylated expanded [n]radialenes (n = 3, 4, 6, 8) 8a-c, 9a-d, and 10a-d with differently functionalized peripheral phenyl rings were prepared and subjected to comprehensive physical-organic study (Fig.…”