Metal‐Free Synthesis of Selenodihydronaphthalenes by Selenoxide‐Mediated Electrophilic Cyclization of Alkynes

Abstract

A transition-metal-free, selenium mediated electrophilic cyclization reaction was realized through a one-pot procedure between simple alkynes and triflic anhydride-activated selenoxides to give selenium containing dihydronaphthalene prod-ucts. This method gave good to very high yields for all products, including selenium-substituted phenanthrene, dihydroquinoline, 2H-chromene, and coumarin, which can be further transformed to other functionalized compounds.

Recyclable iodine-catalyzed radical selenylative annulation of 2-alkynyl biaryls with diselenides in water: a green approach to selanyl polycyclic aromatic hydrocarbons and polycyclic heteroaromatics

“…A wide variety of selanyl PAHs such as phenanthrenes, benzo [c]phenanthrene, benzo[g] chrysene, and dibenzo [ij,no]tetraphene and also selanyl polycyclic heteroaromatics such as naphtho[2,1-b]thiophene and naphtho[2,1-b]furan were synthesized in moderate to excellent yield. In contrast to the previously reported electrophilic (ionic) selenylative annulations of 2-alkynyl biaryls, [16][17][18] we unveiled and proposed that the reaction mechanism operates through a radical pathway but not through a polar (ionic) pathway, as supported by both experimental and computational studies. The in situ formed phenylselenyl iodide (PhSeI) was found to be more reactive than the commercially available PhSeBr or PhSeCl for the synthesis of selanyl PAHs or polycyclic aromatic hydrocarbons.…”

“…Recently, the Li-group reported an electrophilic cyclization of alkynes with triflic anhydride-activated methyl selenoxides and only 9-phenylselanyl-10-phenylphenanthrene was synthesized in 68% yield from 2-( phenylethynyl)-1,1′-biphenyl and phenyl methyl selenoxide (Scheme 1C). 18 The serious limitations associated with this method are the requirement of hazardous reagents in stoichiometric or super stoichiometric amounts, a toxic solvent, specific reaction conditions (−78 °C), moderate yield of product, very low atom economy, generation of hazardous wastes and the requirement of two-step synthesis of phenyl methyl selenoxide from diphenyl diselenide involving hazardous reagents, thus limiting the substrate scope of this method in accessing selanyl PAHs. Hence, developing a green and practical synthetic method for the oxidative selenylative annulation of 2-alkynyl biaryls for accessing selanyl PAHs and polycyclic heteroaromatics is highly desirable.…”

Synthesis of Chalcogenylchromenes through Cyclization of Propargylic Aryl Ethers

“…Compound 8 was prepared according to a published procedure . In a two-mouthed flask (25.0 mL), equipped with a magnetic stirrer were added the 1-phenyl-2-(phenylselanyl)-3 H -benzo­[ f ]­chromene 3a (0.25 mmol, 0.1035 g) and 2.0 mL of DCM.…”

Upper Rim-Bridged Calix[4]arenes via Cyclization of meta Alkynyl Intermediates with Diphenyl Diselenide

“…The formation of product 8b is completely unexpected and to the best of our knowledge, there is no example of similar structures in the literature. The selenium-mediated electrophilic cyclization reaction is well known in the art and has been used to construct a variety of structures [ 19 , 23 , 24 , 25 ]. On the other hand, although the FeCl 3 /Ph 2 Se 2 promoted cyclization of o -alkynyl substituted diaryl methanes (a structural fragment within a calixarene moiety) has been investigated in detail, [ 18 ] the formation of a five-membered product of type 8 has never been observed ( Scheme 5 ).…”