New Reactions of a Dibenzo[a,e]pentalene

Abstract

Reduction of dibenzo[a,e]pentalene 3 (denoted as dibenzopentalene hereafter) with excess lithium gave dilithium dibenzopentalenide 1. Since oxidation of 1 with iodine gave 3, redox behavior between 1 and 3 is controllable and reversible. Reaction of 3 with methyllithium gave lithium 5-methyldibenzopentalenide 5, the formation of which was evidenced by some trapping experiments and X-ray crystallographic analysis. Reactions of 3 with halogens gave 5,10-dihalodibenzopentalenes, 8 and 9. Some optical properties of novel dibenzopentalene derivatives are also demonstrated.

Synthesis and Reactions of Dibenzo[a,e]pentalenes

“…Similar trends were also found in some benzannulated anions [50][51][52][53][54][55][56]. Dianion 26a was also synthesized by the reaction of the corresponding dibenzopentalene 1aa with lithium (Scheme 31) [57]. Oxidation of 26a occurred by treatment with iodine to provide 1aa.…”

“…Very recently, unique reactions of a dibenzopentalene were reported. Dibenzopentalene 1aa reacted with methyllithium to quantitatively produce lithium 5-methyldibenzopentalenide 42, the structure of which was established by X-ray crystallographic analysis (Scheme 34) [57]. Since 6,6-dimethylfulvene derivative reacted with methyllithium to give the corresponding lithium t-butylcyclopentadienide [59], 1aa reacted with methyllithium as a fulvene to give 43.…”

“…Dibenzopentalene 1aa reacted with bromine and iodine to provide the corresponding dihalodibenzopentalenes 1af and 1ag in very high yields (Scheme 35) [57]. Dihalodibenzopentalenes would be good starting compounds for further functionalization of dibenzopentalenes.…”

Pentalenes—From Highly Reactive Antiaromatics to Substrates for Material Science

“…Thus in one of its structurally simplest variants, Saito and co‐workers reduced tris(isopropyl)silylethynylbenzene ( 8 ) with lithium and isolated (besides an open‐chain dimer of 8 ) the dibenzopentalenide 9 , which upon oxidation with iodine provided the dibenzo[ a , e ]pentalene derivative 10 in excellent yield, from which the dihalides 11 were prepared (Scheme ) 5…”

Electron Acceptors Based on an All‐Carbon Donor–Acceptor Copolymer

“…Second, they were often difficult to selectively functionalize after formation of the five‐membered rings. Recent synthetic advances have led to new scalable and functionalizable small‐molecule CP‐PAH systems including indenofluorenes 3 (TIPS=triisopropylsilyl),13a‐c dibenzopentalenes 4 ,14a,b and cyclopenta[ hi ]aceanthrylene units 5 15a–d that show promising electronic and photophysical properties.…”