Generation of an 4‐Isoxazolyl Anion Species: Facile Access to Multifunctionalized Isoxazoles

Abstract

A direct functionalization of unsubstituted isoxazole (1) was achieved by generation of 4‐isoxazolyl anion species (3). An efficient 4‐iodination of isoxazole and halogen–metal exchange reaction using a turbo Grignard reagent (iPrMgCl⋅ LiCl) were essential for the generation of 3, which reacted with various electrophiles to give 4‐functionalized isoxazoles in good to high yields. Isoxazolyl boronate, boronic acid, and stannane were also synthesized as useful building blocks from 1. The current methods enabled us to synthesize multi‐functionalized isoxazoles by introducing each substituent into the desired positions. Furthermore, total synthesis of triumferol, which was isolated from Triumfetta rhomboidea, was achieved from 1 in only three steps.

N‐Chlorosuccinimide‐Promoted One‐Pot Synthesis of Substituted 4,5‐Dihydroisoxazole‐5‐methanols in Aqueous Medium

“…In general, the 1,3‐dipolar cycloaddition reaction has been proven to be very useful for constructing the isoxazole ring [16] . Some commonly used methods for producing isoxazoles include the condensation of primary nitro compounds with terminal acetylenes, [17] cycloisomerization of α,β‐acetylene oximes, [18] and direct functionalization approaches [19] . More recently, Fernandes et al [20] .…”