Regioselective 1,3-Dipolar Cycloaddition Reactions of Unsymmetrical Münchnones (1,3-Oxazolium-5-olates) with 2- and 3-Nitroindoles. A New Synthesis of Pyrrolo[3,4-b]indoles

3-Nitro-1-(phenylsulfonyl)-1H-indole

“…3-Nitroindoles are important building blocks for the synthesis of pyrrolo [2,3-b]indoles and pyrrolo [3,4-b]indoles, via the Barton-Zard pyrrole synthesis (Pelkey et al, 1996;Pelkey & Gribble, 1997), for 1,3-dipolar cycloaddition reactions with azomethine ylides and mesoionic mü nchnones (1,3-oxazolium-5-olates) (Gribble et al, 1998(Gribble et al, , 2000. Furthermore, the chemistry of these electron-deficient 3nitroindoles is of great interest and utility for the synthesis of carbazoles via Diels-Alder cycloaddition reactions (Wenkert et al, 1988;Kishbaugh & Gribble, 2001;Biolatto et al, 2001), for nucleophilic reactions and for reduction to aminoindoles (Roy & Gribble, 2006).…”

The Generation of Indole-2,3-quinodimethanes from the Deamination of 1,2,3,4-Tetrahydropyrrolo[3,4-b]indoles

“…In continuation of our synthesis and chemistry of pyrrolo [3,4-b]indoles [16][17][18][19][20][21][22], we now report the first generation of an indole-2,3-quinodimethane (1) species from the pyrrolo [3,4-b]indole (2) ring system (Figure 1). Given the availability of pyrrolo [3,4-b]indoles and, in particular, 1,2,3,4tetrahydropyrrolo [3,4- Moreover, the early work of Lemal and McGregor on the generation of dienes via the stereospecific deamination of 3-pyrrolines with Angeli's salt (Scheme 1) proffered the feasibility of our concept [23,24].…”

“…Indole 14 was obtained as a yellow oil (0.03 g, 0.09 mmol, 27%, 2 steps): 1 H-NMR (CDCl 3 ) δ 8.23 (d, 1H, J = 7.5 Hz), 7.73 (d, 3H, J = 7.5 Hz), 752 (t, 1H, J = 7.5 Hz), 7.40 (t, 2H, J = 7.5 Hz), 7.33-7.26 (m, 2H), 6.76 (q, 1H, J X = 11.5 Hz), 5.75 (dd, 1H, J M = 17.5 Hz), 5.45 (dd, 1H, J A = 11.5 Hz), 3.11 (q, 2H, J = 7.5 Hz), 1.32 (t, 3H, J = 7.5 Hz); 13 C-NMR (CDCl 3 ) δ 133.8 (2C), 129.4 (3C), 127.7, 126.4 (3C), 124.5 (2C), 124.0, 119.9, 116.9, 115.2 (2C), 20.1, 15.5; HRMS calcd for C 18 H 17 O 2 NS: 311.0980; Found: 311.0977.2.12. 2,3-Dimethyl-1-(phenylsulfonyl)indole(19)…”

Microwave-assisted synthesis of pyridylpyrroles from N-acylated amino acids

“…17 Mesoionic azomethine ylide-type dipoles can be obtained from N-acylated amino acids with a dehydrating agent. Typically the water-removing agent has been acetic anhydride used simultaneously for the acylation of the amino acid, but other reagents, such as N,N 0 -dicyclohexylcarbodiimide (DCC), 18 19 and N,N 0 -diisopropylcarbodiimide (DIC), 20 have been used for the dehydration of N-acylated amino acids in the cycloaddition. The chemistry of the mü nchnones and azlactones has recently been reviewed, 21 and some mesoion-mediated syntheses of pyrroles have also been reported, 22 including one microwave-assisted synthesis.…”