Electrophilic Cyclizations of Diaryl-2,3-allenyl Ethers withN-Bromosuccinimide: En Route to 2-Bromonaphthalenes

Abstract

The reaction of diaryl-2,3-allenyl ethers with N-bromosuccinimide in a mixed solvent of CH3NO2/EtOH affords highly functionalized 2-bromonaphthalenes in 21-66% yields. The electronic effect on the aryl is important to the selectivity of the reaction: when 4-(trifluoromethyl)phenyl or 1-naphthyl was applied as one of the two aryl groups, the regioselectivity was practical, affording the products with the other relatively electron-rich phenyl ring or the non-1-naphthyl group being cyclized as the major, respectively.

Palladium-Catalyzed Cleavage of α-Allenylic Aryl Ether toward Pyrazolemethylene-Substituted Phosphinyl Allenes and Their Transformations via Alkenyl C–P(O) Cleavage

“…The importance of allenes necessitates extensive explorations on their transformations and synthesis during the past two decades . On one side, various transformations from allenes to other functionalities have been demonstrated including transition-metal catalyzed intermolecular/intramolecular cycloaddition, nucleophilic addition, oxidative carbocyclization, and others. − The importance of allene moieties has, on the other hand, stimulated substantial interest in constructing versatile allene compounds. Traditional methods to prepare allenes generally lie on monoalkenes, conjugated enynes, alkynes, cyclopropanes, and propargylic fragments as starting materials. , Due to the unique activity of cumulate diene, direct functionalization of allenes to obtain allenes is appealing ,, but challenging, which would include maintenance of the 1,2-diene moiety against forming alkenes in the presence of a transition-metal catalyst and electrophilic/nucleophilic reagents, generally via the generation of π-allylmetal species followed by a β-hydride elimination process.…”

Synthesis of Polysubstituted 2-Iodoindenes via Iodonium-Induced Cyclization of Arylallenes

“…Formation of an iodonium ion D upon further reaction of C with a second equivalent of cationic iodine atom followed by anti 5-endo nucleophilic attack of the aryl group gives the functionalized 2-iodoindene 2 . Considering the versatility of the carbocyclization reactions promoted by halogen electrophiles and prior reports in the literature illustrating the possibility to activate allene unsaturations with halogen electrophiles toward anti nucleophilic arylation reactions, we decided to investigate the formation of 2-iodoindenes 4 using an unprecedented methodology based on the electrophilic iodocarbocyclization of tri- and tetrasubstituted arylallenes 3 (Scheme , eq 2).…”