A Tandem Ring‐Opening/Michael Addition/Ring‐Closure Sequence for the Regiospecific Synthesis of 5‐Hydroxy‐4,5‐dihydroisoxazoles

Abstract

An effective and highly regiospecific strategy for the synthesis of 5-hydroxy-4,5-dihydroisoxazoles is described via a tandem reaction including ring-opening, Michael addition, and ring-closure in one pot under mild conditions. Diverse structural 5-hydroxy-4,5-dihydroisoxazoles were afforded in up to 96% yield for 21 examples. This strategy is highly efficient, environmentally friendly, and metal free.[a] Dr. d, J = 22.0 Hz, 2 C), 107.8, 49.0. HRMS m/z (ESI) calcd for C 15 H 12 FNO 2 , (M + Na) + 280.0744; found, 280.0743.

TEMPO‐Mediated Selective Synthesis of Isoxazolines, 5‐Hydroxy‐2‐isoxazolines, and Isoxazoles via Aliphatic δ‐C(sp3)‐H Bond Oxidation of Oximes

“…Thus, these scaffolds could take part in hydrogen bonds, donor‐acceptor interactions with various enzymes and receptors [6] . Currently, various life‐saving drugs contain isoxazoles and isoxazolines moieties (Figure 1A) [7] and 5‐hydroxy‐2‐isoxazolines have been utilized as a versatile synthon possibly because it can be easily transformed into various functional groups like isoxazoles, β ‐enaminones, 1,3‐diketones, γ ‐amino alcohols, and N ‐aryl‐ β ‐lactams, etc [8–10] . Isoxazoles are also extensively used as 1,3‐dicarbonyl equivalents in natural product synthesis [11] .…”