Synthesis of divergent benzo[b]fluorenones through cycloaromatization reactions of 1,5-enynols and 1,5-diynols
A facile and efficient synthesis of divergent benzo[b]fluorenones is described through the use of dichlorobenzoquinone-promoted oxidative cycloaromatization reactions of acyclic 1,5-enynols and 1,5-diynols. The success of these cascade reactions depends on the chemoselectivity of the initial Meyer-Schuster rearrangement to produce allenol intermediate, which is followed by regioselective Schmittel cyclization and the subsequent Friedal-Crafts alkylation or radical attack at the terminal Ar moiety. Only an oxidant and a solvent were required in the reaction, thus delivering a small library of the expected polycarbocyclic products with excellent functional group tolerance under metal-free conditions. The absorption and photoluminescence properties of the selected benzo[b] fluorenones were also investigated. The results indicated that the compound (2h) which contained an electron-donating 4-OMe group at the phenyl moiety displayed deep green color emission (491 nm).
Yan, Bingyu,Fu, Yang,Zhu, Hui,Chen, Zhiyuan
p. 4246 - 4262
(2019/03/26)
The first aryne evolution from the reactions of selenonium salts with aryllithiums
The first example of the benzyne generation was found in the reactions of alkynylselenonium salt 1a with 1.0 equiv. of phenyllithium in THF at room temperature for 3 h. The formation of the aryne intermediate was confirmed in the reactions of alkynylselenonium salt 1b and tri-p-tolylselenonium salt 6b with tolyllithium, which gave a mixture of alkynylbiphenyl derivatives 18 and 19 in 19% yield (18:19=11:8) and a mixture of bitolyls 28 and 29 in 63% yield (28:29=2:1), respectively. The reaction mechanisms of these reactions are discussed. (C) 2000 Elsevier Science Ltd.