Copper-Catalyzed Domino Synthesis of 2-Arylthiochromanones through Concomitant C–S Bond Formations Using Xanthate as Sulfur Source

Abstract

An efficient domino process for the synthesis of thioflavanones has been described using a copper catalyst without addition of any external ligand. A variety of thioflavanones have been synthesized from easily accessible 2'-iodochalcones or 2'-bromochalcones in excellent yield through in situ incorporation of sulfur using xanthate as an odorless sulfur source. This domino process proceeds through Cu-catalyzed C(aryl)-S bond formation by the coupling reaction of xanthate with 2'-halochalcones followed by C-S bond cleavage of thioester then S-C bond formation by intramolecular Michael addition.

Syntheses and Excited‐State Intramolecular Proton Transfer of 3‐Hydroxythioflavone and Its Sulfone Analogue

“…The new synthetic strategy involved reaction of 2′‐iodoacetophenone with benzaldehyde in the presence of sodium hydroxide, affording (E)‐2′‐iodochalcone 4 in 78 % yield. Then two C−S bonds formation was performed successfully with potassium ethyl xanthate as the sulfur source . Treatment of 4 with 2 equivalents of xanthate and 10 mol % copper acetate as a catalyst afforded 2‐phenylthiochroman‐4‐one ( 5 ) in 89 % yield.…”

“…Then two CÀS bonds formation was performed successfully with potassium ethyl xanthate as the sulfur source. [15] Treatment of 4 with 2 equivalents of xanthate and 10 mol % copper acetate as a catalyst afforded 2-phenylthiochroman-4-one (5) in 89 % yield.…”

Elemental‐Sulfur‐Promoted C(sp3)−H Activation of Methyl Heteroarenes Leading to Thioamides

“…Elemental sulfur and its derivatives are promisingc andidates for single electron transfer reagents and can participate in redox reactions. [14,15] Because elemental sulfur could exist in variouso xidation states, it could promote the production of methyl heteroarene radicals. [14c] Methyl heteroarenes have the potentialt or eadily reactw ith N, N-dimethylformide (DMF) with the aid of elemental sulfur to form the substituted thioamide under mild condition (Scheme1).…”

ChemInform Abstract: Palladium‐Catalyzed Carbonylative Four‐Component Synthesis of Thiochromenones: The Advantages of a Reagent Capsule.

“…[10] Furthermore,t he oxidized variants of thiochromen-4-ones are used as human cytomegalovirus protease inhibitors [11] and photolabile protecting groups for phosphate compounds. [14] Thep reviously reported methods generally suffer from drawbacks related to synthetic efficiency,a vailability or diversity of the substrates,r egioselectivity,a nd functional-group compatibility.I nt heory,o ur proposed carbonylative four-component one-pot reaction is af airly efficient pathway that provides the desired products from commercially available odorless materials with ar educed number of manual operations (Scheme 1). [14] Thep reviously reported methods generally suffer from drawbacks related to synthetic efficiency,a vailability or diversity of the substrates,r egioselectivity,a nd functional-group compatibility.I nt heory,o ur proposed carbonylative four-component one-pot reaction is af airly efficient pathway that provides the desired products from commercially available odorless materials with ar educed number of manual operations (Scheme 1).…”

“…Conversely,w hen Na 2 S·9 H 2 Ow as employed without the capsule,n od esired product, but only side product bis(2-phenylvinyl)sulfide,w as generated (entry 2). For the leaving group,f luorine showed better reactivity in the S N Ar process than the chlorine,b romine,a nd methoxy counterparts (entries [14][15][16]. Among various solvents,M eCN proved to be the most suitable medium (entries 6-9).…”