Higher-order [10 + 2] cycloaddition of 2-alkylidene-1-indanones enables the dearomatization of 3-nitroindoles: access to polycyclic cyclopenta[b]indoline derivatives

Abstract

A dearomative higher-order [10+2] cycloaddition reaction of 3-nitroindoles and 2-alkylidene-1-indanones was developed. Using TEBA as the phase-transfer catalyst, a wide range of structurally diverse polycyclic cyclopenta[b]indoline derivatives were obtained in...

Copper-Catalyzed Asymmetric Dearomative [3+2] Cycloaddition of Nitroheteroarenes with Azomethines

“…Based on our experimental results and previous related reports [ 27 , 28 , 29 , 30 , 31 , 37 , 38 , 39 , 40 ], a plausible catalytic mechanism involving a stepwise reaction process was assumed to explain the stereoselectivity of the asymmetric dearomative [3+2] cycloaddition of α -imino γ -lactones with electron-deficient nitroheteroarenes ( Scheme 5 ). For the reaction with 3-nitroindoles as partners, the in situ-formed azomethine ylide 2a’ is coordinated to the chiral CuL* complex, leading to the active species A .…”

“…α -Imino γ -lactones as azomethine ylide precursors have proven to be a type of efficient 1,3-dipole that could be used in catalytic enantioselective [3+2] cycloadditon reactions with various dipolarophiles for the construction of spirocyclic butyrolactone–pyrrolidine skeletons [ 37 , 38 , 39 , 40 ]. Enlightened by the previous works on the asymmetric cycloaddition reaction with α -imino γ -lactones as 1,3-dipoles, we speculated that the asymmetric dearomative cycloaddition reaction of α -imino γ -lactones and electron-deficient nitroheteroarenes would take place in the presence of a suitable chiral copper complex as the catalyst.…”

Annulations involving 1-indanones to access fused- and spiro frameworks

“…Very recently, dearomative [10+2] cycloaddition of 2-arylidene-1-indanones 49 and 3-nitroindoles 62 at ambient temperature was developed. 49 This transformation was attained using triethyl benzyl ammonium chloride (TEBA) as phase transfer catalyst under basic conditions (Na 2 CO 3 ) to afford wide range of polycyclic cyclopenta[ b ]indolines 63 in excellent yields and diastereoselectivity (up to 99% yield and >20 : 1 dr). 3-Nitroindoles bearing electron-withdrawing and donating substituents (F, Cl, Br, CN, Me) were well tolerated with the catalytic system.…”

A regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins to access indanone-fused 2D/3D skeletons

“…Notably, 2-benzylidene-1-indenones, which have rich reactive sites, have been commonly employed as C2 units at the C2- and C4-positions for the [2 + 1]/[2 + 3]/[2 + 4] cycloaddition reaction to generate spiro indanone compounds (Scheme 2b, eqn (1)). 8 However, 2-benzylidene-1-indenones have rarely been employed as C3 units at the C3- and C4-positions for the construction of fused indanones to form a C ring except for the example of dimerization of 2-benzylidene-1-indenones, 9 which is even more uncommon. With the 2-benzylidene-1-indenones as C3 units to form fused indanones, we speculated that the [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones would lead to a new method for the construction of fused indanones and assemble diverse functional groups in the formed fused indanones, which is different from the traditional B ring formation method (Scheme 2b, eqn (2)).…”