77507-55-2Relevant academic research and scientific papers
Regioselective 1,3-dipolar cycloaddition reactions of unsymmetrical munchnones (1,3-oxazolium-5-olates) with 2- and 3-nitroindoles. A new synthesis of pyrrolo[3,4-b]indoles
Gribble, Gordon W.,Pelkey, Erin T.,Simon, Wendy M.,Trujillo, Hernando A.
, p. 10133 - 10140 (2007/10/03)
The unsymmetrical mesoionic munchnones 13 (3-benzyl-2-methyl-4-phenyl-1,3-oxazolium-5-olate) and 14 (3-benzyl-4-methyl-2-phenyl-1,3-oxazolium-5-olate) react with the N-protected 2- and 3-nitroindoles 1 (ethyl 2-nitroindole-1-carboxylate), 6 (3-nitro-1-(phenylsulfonyl)indole), and 17 (ethyl 3-nitroindole-carboxylate) in refluxing THF to afford in good to excellent yields the pyrrolo[3,4-b]indoles 15 (2-benzyl-1-methyl-3-phenyl-4-carboethoxy-2,4-dihydropyrrolo[3,4-b]indole), 16 (2-benzyl-3-methyl-1-phenyl-4-carboethoxy-2,4-dihydropyrrolo[3,4-b]indole), 18 (2-benzylmethyl-3-phenyl-4-(phenylsulfonyl)-2,4-dihydropyrrolo[3,4-b]indole), and 19 (2-benzyl-3-methyl-1-phenyl-4-(phenylsulfonyl)-2,4-dihydropyrrolo[3,4-b]indol e). In several cases the regiochemistry, which is opposite to that predicted by FMO theory, is very high and leads essentially to a single pyrrolo[3,4-b]indole; e.g., 6+ 13→19 in 74% yield. (C) 2000 Elsevier Science Ltd.
