Synthesis of enantiopure furo[2,3-b]pyrroles

Natural Product-Derived Chiral Pyrrolidine-2,5-diones, Their Molecular Structures and Conversion to Pharmacologically Important Skeletons

“…12,35,36 When the pyrrolidine-2,5-dione 13e was used, a 5-exo-trig cyclization occurred in the N-acyliminium ion, using 10 equiv of NaBH 4 in EtOH, followed by acidic workup (5 M HCl), resulting in the exclusive formation of furo[2,3-b]pyrrole 16b. 34 However, when the aryl ring bears electron-donating groups, it competes with the hydroxy group acting as a nucleophile for the N-acyliminium cyclization. Thus, the p y r r o l i d i n e -2 , 5 -d i o n e s 1 3 c a n d 1 4 a f u r n i s h e d tetrahydropyrrolo[2,1-a]isoquinolinones 15 and 17 via a 6endo-trig Pictet−Spengler cyclization in excellent yield.…”

“…Methyl (S)-2-[(S)-1-benzyl-3-hydroxy-2,5-dioxopyrrolidin-3-yl]-2hydroxyacetate (13a). 34 General Procedure for the Preparation of Furopyrrolone Analogues 16, 18, 20, and 22. To a stirred solution of pyrrolidine-2,5-dione 13c/13d/14a/14b (1 mmol, 1 equiv) in absolute EtOH (10 mL) precooled to 0 °C was added excess NaBH 4 (10 equiv) with stirring.…”

I 2 -catalyzed one-pot synthesis of benzofuro/thieno[2,3- b ]pyrrole motifs

“…Infrared spectra were determined on an Agilent Cary 630 FT-IR spectrophotometer. 1 H NMR (400 MHz) and 13 C NMR (100 MHz) spectra were obtained on Bruker WH-200 spectrometer, Agilent spectrometer and JEOL spectrometer using CDCl 3 (proton d 7.26 and carbon d 77.23) as solvent and TMS (d ¼ 0.00 ppm) as an internal standard at room temperature. Chemical shifts were expressed in parts per million (ppm) and coupling constant (J) in hertz (Hz).…”

“…11 Considering these impressive biological and chemophysical properties of pyrrole derivatives and their significant role in organic synthesis, the development of versatile, convenient, and efficient methods for the synthesis of these core moieties has been attracted considerable attention from both the academic and industrial communities. The classical routes to pyrrole-fused heterocyclic system proceeded from the (i) reaction of O-phenyl-conjugated oxime ether with an alkyl radical, 12 (ii) Baldwin's cyclization of 3-substituted pyrrolidinediones, 13 (iii) thermolysis of the methyl 2-azido-3-(3-furyl)propenoate, 14 (iv) reaction between 1,2-diaza-1,3-butadienes and diethyl or dimethyl acetylsuccinate, 15 (v) Gewald reaction of 1,3-dicarbonyl compound, alkyl or aryl isothiocyanates via ketene N,S-acetal intermediate, followed by a Dieckmann type cyclization, 16 (vi) reductive cyclization of 3-(2-nitrophenyl)thiophenes via nitrene intermediates, 17 (vii) radical or palladium catalyzed cyclization of 3-(2-bromoindol-3-yl)acrylonitriles. 18 Despite these advances, to the best of our knowledge, the utilization of three-component domino reaction strategy for the construction of furo[2, 3-b]pyrroles and thieno[2, 3-b]pyrroles has not yet been documented.…”

“…Scheme 1. Plausible mechanism for the synthesis of 4a -t. J ¼ 9.6 Hz, Ar-H), 8.37 (d, 1H, J ¼ 10 Hz, Ar-H) ppm;13 C NMR (CDCl 3 , 100 MHz) d: 27.…”