title: Palladium-catalyzed annulation of 9-halophenanthrenes with alkynes: synthesis, structural analysis, and properties of acephenanthrylene-based derivatives.
abstract: The palladium-catalyzed annulation of 9-bromo- and 9-chlorophenanthrenes with alkynes gave 4,5-disubstituted acephenanthrylenes in yields of 58-95% (9 examples). Asymmetric alkynes, such as 1-phenyl-1-propyne, 1-phenyl-1-hexyne, and 1-cyclopropyl-2-phenylethyne, regioselectively form (cyclo)alkyl-substituted products, following the regular rule that governs the carbopalladation of alkynes. This synthetic protocol can also be utilized in annulations with several π-extended bromoarenes, such as 7-bromo[5]helicene, 5-bromo[4]helicene, 9-bromoanthracene, 3-bromoperylene, and 3-bromofluoranthene, to give the corresponding annulated products in moderate to good yields (51-86%; 6 examples). Similarly, bromocorannulene produced highly curved 1,2-disubstituted cyclopentacorannulenes. Reactions of 6,12-dibromochrysene and 4,7-dibromo[4]helicene with di(4-tolyl)ethyne provided the twofold annulated products in moderate yields. 4,5-Diphenylacephenanthrylene and 6,7-diphenylbenzo[a]acephenanthrylene thus generated were converted into phenanthro[9,10-e]acephenanthrylene and benzo[a]phenanthro[9,10-e]acephenanthrylene, respectively, by oxidative cyclodehydrogenation. The structures of 4,5-diphenylacephenanthrylene, 4,5-diphenyldibenzo[a,l]acephenanthrylene, 1,2-diarylcyclopentacorannulenes, and benzo[a]phenanthro[9,10-e]acephenanthrylene were verified by X-ray crystallography. The photophysical and electrochemical properties of the selected annulated products were investigated.
authors: Department of Chemistry, National Cheng Kung University, No.1 Ta-Hsueh Road, 70101 Tainan (Taiwan).
authors: En-Chih
authors: EC
authors: Liu
authors: Min-Kuan
authors: MK
authors: Chen
authors: Jen-Yi
authors: JY
authors: Li
authors: Yao-Ting
authors: YT
authors: Wu
keywords: alkynes; annulation; macrocycles; palladium; synthesis design