The [4+3] annulation reaction of crotonate-derived sulfur ylides with thioaurones has, for the first time, been reported using NaH as the base. A diverse array of 2,5-dihydrobenzo[4,5]thieno[3,2-b]oxepines is obtained in good to excellent yields. The proposed mechanism is investigated and supported by DFT calculations.
Solvent-controlled switchable domino reactions between 2-alkylidenebenzothiophene-3(2H)-ones and Morita-Baylis-Hillamn (MBH) carbonate were developed. All domino reactions exhibited excellent regioselectivity, producing a broad spectrum of benzothiophene-fused α-pyran, 2,3-dihydrooxepine, and oxatricyclodecene derivatives. Furthermore, [4 + 2], [4 + 3], and related domino reactions from identical substrates can be controlled.
A protocol for the direct functionalization of N-H/α,α,β,β-C(sp)-H of piperidine without any metal or external oxidants is reported. This reaction is promoted by 4-(trifluoromethyl)benzoic acid via an azomethine ylide intermediate. This is a simple method for the synthesis of spirooxindoles bearing 3-substituted oxindole moieties.
AC s 2 CO 3 -promoted Michael addition-[2,3]-sigmatropic rearrangement dominor eaction between arenesulfonylindolea nd sulfur ylide hasb een developed. This reaction affords af acile methodf or the synthesis of 3-substituted indoles with ah omoallyl sulfide moiety.I nt his domino sequence, two CÀCb onds and one CÀCb ond cleavage were formed.
Spirooxindoles bearing a1 -azabicyclo[5.3.0]decane moiety were synthesized in one step via direct functionalizationo ft he azepane withoutatransition metal or oxidants. This is an efficient process for the synthesiso f fused 7/5-heterobicyclic systemsi no ne step. Furthermore, cycloaddition of the in-situ-generated azomethine ylide only proceededfor alkenyls ulfone dipolarophiles.
A 1,4-diazabicyclo[2.2.2]octane (DABCO)-catalyzed [4+2] annulation reaction between 2-alkylidenebenzothio phene-3(2H)-ones and allenoate has been developed. The substrate scope includes both electron-withdrawing and electron-donating groups on the benzothiophene moiety. This method can be carried out under mild conditions and gives a wide range of highly functionalized benzothiophene-fused γ-pyran derivatives in good yields with moderate selectivity.
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