Dilithium anthracene

Dehydrobenzene or benzyne 158 can be trapped by all manner of species. 1,2-Dehydro-o-carborane 159 has been shown to undergo many of the same reactions as its two-dimensional relative, 1,2-dehydrobenzene. Although dehydroaromatic molecules can be formed in a variety of ways, synthetic pathways to 1,2-dehydro-o-carborane are quite limited. An effective procedure reported so far78 first forms the dianion by deprotonation of o-carborane with 2 equiv. of butyllithium. Precipitated dilithium carborane is then treated with 1 equiv. of bromine at 0°C to form the soluble bromo anion 160. Thermolysis of 160 with anthracene, furan, and thiophene as substrates leads to the adducts 161-164.79 80 1,2-Dehydro-o-carborane reacts with norbomadiene to give both homo 2+4 and 2+2 addition, leading to three products 165-167, in a 7 1 ratio79. An acyclic diene, 2,3-dimethyl-... 

H and C NMR spectra were applied to elucidate the electronic structure of the dianions in the dilithium arene compounds formed with anthracene, phenanthrene and 1,2,3,4-dibenzocyclooctatetraene (115). Although the three dianions have 16- 7r isoelec-tronic systems, the former two differ due to their charge distributiou, and 115 due to the steric strain in the cyclooctane ring, interfering with a coplanar configuration... 

The second equilibrium ion-pah acidity constant (pKi) of 9,10-dihydrodibenz[a,/i]-anthracene (DBDHA) (2) in THF at 298 K has been found to be considerably lower than for other 9,10-dihydroanthracene (DHA) derivatives and the dependence on the counter ions sodium (pAA 28.5) and potassium (pAA 30.4) is less marked as a consequence of extended p. re-conjugation of the dianion (3) with the outer benzene rings.5 The disodium, dipotassium, and dirubidium salts exist as contact ion triplets and the dilithium salt as a solvent-separated triplet. 

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