Synthesis of Indolines, Indoles, and Benzopyrrolizidinones from Simple Aryl Azides

Abstract

A simple approach to prepare indolines and benzopyrrolizidinones from ortho-azidoallylbenzenes via a tandem radical addition/cyclization is described. The use of triethylborane to initiate and sustain the process provides the best results. Indolines are easily converted into the corresponding indoles by oxidation with manganese dioxide.

Pentacoordinated Carboxylate π‐Allyl Nickel Complexes as Key Intermediates for the Ni‐Catalyzed Direct Amination of Allylic Alcohols

“…4‐Cinnamylpyrrolidine ( 3 dn ):31 1 H NMR (400 MHz, CDCl 3 , 30 °C): δ =7.39–7.20 (m, 5 H, aromatic), 6.54 (d, J =15.8 Hz, 1 H, C H CHCH 2 ), 6.34 (td, J =15.8, 6.7 Hz, 1 H, CHC H CH 2 ), 3.28 (d, J =6.7 Hz, 2 H, CHC H 2 N), 2.59 (br s, 4 H, NC H 2 CH 2 ), 1.84–1.80 ppm (m, 4 H, NCH 2 C H 2 ); 13 C NMR (100 MHz, CDCl 3 , 30 °C): δ =127.3, 132.2, 128.7, 127.6, 127.5, 126.5, 58.5, 54.2, 23.7 ppm.…”

“…All 19 FNMR chemical shifts were recorded in ppm (d) relative to fluorine resonance in a,a,a-trifluorotoluene as an external standard at d = À63.90 ppm. 31 P{ 1 H} NMR chemical shifts were recorded in ppm (d)r elative to 85 %H 3 PO 4 as external standard at d = 0.00 ppm. HPLC spectra were recorded on aJ ASCO UV-2075 and PU-2089.…”

“…We also tried to measure the NMR spectrum at À30 8C; however,t his also failed due to ap recipitation of the compound. 31 [(h 3 -allyl)Ni(dppf)Cl] (8): As olution of allyl chloride (60.1 mg, 0.60 mmol) in toluene (5 mL) was added slowly to as olution of [Ni(cod) 2 ]( 138 mg, 0.50 mmol) and dppf (277 mg, 0.50 mmol) in toluene (20 mL) at room temperature. The formation of brown crystals was observed, which were collected after 12 hb yf iltration to give 8 (343 mg, 0.50 mmol, 100 %).…”

Recent Advances in Reactions of Azides

“…As previously reported, Et 3 B is proposed to act as a radical initiator and a chain propagator. When the halogen reagent combines with Et 3 B, an approach to prepare indolines from ortho ‐azidoallylbenzenes via a tandem radical addition/cyclization can be achieved . Its formation is optimal when 1 equiv.…”

Construction of Unusual Indole-Based Heterocycles from Tetrahydro-1H-pyridazino[3,4-b]indoles

“…With this failure in hand, we first turned our attention to the crucial C2-C3 indole oxidation step. A variety of oxidizing agents (e.g., DDQ [ 33 ], BQ, NBS/TBPB, MnO 2 [ 34 , 35 , 36 ], Na 2 Cr 2 O 7 , I 2 , PCC [ 37 ], Pd/C [ 38 ], CAN [ 39 ] and CuCl 2 ∙2H 2 O [ 40 ]) was investigated ( Table 1 ). Common reagents such as BQ, Na 2 Cr 2 O 7 , PCC, Pd/C, I 2 , and NBS in combination with TBPB, although frequently used for oxidation of the indoline ring, proved unsuccessful.…”