An expedient regio and diastereoselective synthesis of novel spiropyrrolidinylindenoquinoxalines via 1,3-dipolar cycloaddition reaction

Recent advances in the transition-metal-free synthesis of quinoxalines

“…This can be attributed based on the fact that in 158, the 3-methyl-4nitroisoxazoles core is positioned closer to the dipolar region that is opposite in 158 0 . 132 Recently, a transition-metal-free one-pot domino process for the synthesis of diverse pyrrolo/indolo[1,2-a]quinoxaline derivatives has been realized by Mandal and Pramanik (Scheme 46). 133 By using 50 mol% of p-TsOH as the catalyst, a threecomponent reaction of N-(2-aminophenyl)pyrroles/indoles 159, with various cyclic 1,2-dicarbonyl compounds 160 or 163 and alcohols 161 or aliphatic amines 166 were performed in open-air heating condition.…”

Recent applications of ninhydrin in multicomponent reactions

“…Chowhan and co-workers accomplished a similar type of isoxazole pendant compound 102 through a four-component reaction with high regio-and diastereoselectivity. 114 They incorporated benzylamine 6, ninhydrin 1, PDA 77 and isoxazole derivatives 100 to achieve the desired product 102 via the 1,3dipolar [3 + 2] cycloaddition reaction. In particular, the nature of the substitution and their position on the aromatic rings of styrene (dipolarophile), benzylamines and PDA control the diastereoselectivity of the reaction (Scheme 31).…”

Advances in the Synthesis of Benzo‐Fused Spiro Nitrogen Heterocycles: New Approaches and Modification of Old Strategies

“…An attempt to introduce 4-nitroortho-phenylenediamine into this reaction was unsuccessful; reaction product 276 was not obtained (Scheme 72). [278] The multicomponent condensation, 1,3-dipolar cycloaddition reactions of ninhydrin 273, ortho-phenylenediamine 275, amino acids 277, 3-cyanoacetylindoles 278 and arylaldehydes 279 are also efficient for the preparation under mild conditions of spiro-fused indenoquinoxaline-11,2-pyrrolidines (R 2 , R 3 = H) or pyrrolizidines (R 2 + R 3 = CH 2 CH 2 CH 2 ) 280. The initial condensation reaction of ninhydrin with diamine led to indenoquinoxaline 281, in the interaction of which with the amino acid, as in the case of isatins, azomethine ylide 282 was generated.…”

“…An attempt to introduce 4‐nitro‐ ortho ‐phenylenediamine into this reaction was unsuccessful; reaction product 276 was not obtained ( Scheme 72). [278] …”