Dehydroannulenes perethynylated

4 Perethynylated Dehydroannulenes and Expanded Radialenes Large Carbon Cores on the Way to All-Carbon Sheets 

Since tetraethynylethenes represent a repeat unit in more than one two-dimensional carbon network including 45 and 46 (Fig. 13-1) [1] the preparation of a specific network cannot be accomplished by simple oxidative polymerization of 20, but rather requires a more characteristic macrocydic precursor as starting material. Macrocyclic precursors to extended carbon sheets are perethynylated dehydroannulenes [56] and expanded radialenes, novel carbon-rich materials with interesting and unusual structures and functions. 

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Molecular scaffoldings with tetraethynylethenes (TEEs, 3,4-diethynylhex-3-ene-l,5-diynes) and trans-1,2-diethynylethenes [DEEs, (E)-hex-3-en-l,5-diynes] are at a particularly advanced stage.114,37 38 441 A collection of dose to one hundred partially protected and functionalized derivatives have been prepared in the meantime, providing starting materials for the perethynylated dehydroannulenes and expanded radialenes shown in Figure 6.136 441 TEEs and DEEs, as well as dimeric derivatives substituted at the terminal alkynes with donor (D, p-(dimethyl-... 

Based on either cis-substituted or geminally substituted TEE derivatives, two families of macrocycles have been constructed, namely perethynylated dehydroannulenes and expanded... 

Huckel aromaticity upon reduction, whereas 26b gains aromaticity (4n + 2, n — 3) when converted to its dianion. The effect of substituting the peripheral silyl groups by aromatic groups still needs to be explored for these perethynylated dehydroannulenes. 

Scheme 13-10 Preparation of perethynylated dehydroannulene precursors to planar all-carbon networks.

Kivala M, Mitzel F et al (2006) Two-dimensional acetylenic scaffolding extended donor-substituted perethynylated dehydroannulenes. Chem Asian J 1 479 89 Nielsen MB, Diederich F (2005) Conjugated oligoenynes based on the diethynylethene unit. Chem Rev 105 1837-1867... 

Fig. 6. Planar, perethynylated aromatic (27a,b) and anti-aromatic (26a,b) dehydroannulenes [30].

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