N‐Bromosuccinimide‐Mediated Radical Cyclization of 3‐Arylallyl Azides: Synthesis of 3‐Substituted Quinolines

Abstract

Visible light irradiation of N‐bromosuccinimide serves as an effective means to convert methyl 2‐(azidomethyl)‐3‐arylpropenoates and 2‐(azidomethyl)‐3‐arylacrylonitriles to the corresponding iminyl radicals via α‐hydrogen abstraction and subsequent extrusion of dinitrogen. Thus formed iminyl radicals then undergo intramolecular ortho attack on the aryl ring, affording methyl quinoline‐3‐carboxylates and quinoline‐3‐carbonitriles respectively.magnified image

Synthesis of quinoline-3-carboxylates by a Rh(II)-catalyzed cyclopropanation-ring expansion reaction of indoles with halodiazoacetates

“…The yields of ethyl quinoline 3-caboxylates we obtained by using our method (Table 1) compares favorably with three recently published methods where arylmethyl azides [22], arylallyl azides [23] and o -nitrobenzaldehydes [24] were used as starting materials.…”

Synthesis of 3,4,5‐Trisubstituted Isoxazoles from Morita–Baylis–Hillman Acetates by an NaNO2/I2‐Mediated Domino Reaction

“…accomplished the synthesis of quinolones from allyl azides by cyclization of iminyl radicals generated by N-bromosuccinimide in light. [12] These results inspired us to examine the reaction of the MBH acetate A with NaNO 2 and I 2 since we anticipated that aM ichael reaction with A would afford the allyl nitro derivative B,which would undergo intramolecular cyclization to offer the alkyl 1-nitro-3a,7a-dihydro-1Hindene-2-carboxylate E (Scheme 1). To test the hypothesis, the MBH acetate 1ab was treated with NaNO 2 (1.0 equiv) and iodine (1.0 equiv) at room temperature in DMF.T he reaction was complete in 1hour, thus affording as olid product in 40 %y ield.…”

Synthesis of 3,4,5‐Trisubstituted Isoxazoles from Morita–Baylis–Hillman Acetates by an NaNO2/I2‐Mediated Domino Reaction

“…Later, Yu et al. accomplished the synthesis of quinolones from allyl azides by cyclization of iminyl radicals generated by N ‐bromosuccinimide in light 12. These results inspired us to examine the reaction of the MBH acetate A with NaNO 2 and I 2 since we anticipated that a Michael reaction with A would afford the allyl nitro derivative B , which would undergo intramolecular cyclization to offer the alkyl 1‐nitro‐3 a ,7 a ‐dihydro‐1 H ‐indene‐2‐carboxylate E (Scheme ).…”