Cascade Formation of Isoxazoles: Facile Base‐Mediated Rearrangement of Substituted Oxetanes

Abstract

Give me five! Nitro compounds and oxetan‐3‐one react through an intriguing cascade sequence to give isoxazole‐4‐carbaldehydes using inexpensive reagents in a one‐pot procedure (see scheme; Ms=methanesulfonyl). A variety of 3‐substituted isoxazole‐4‐carbaldehydes were obtained in high overall yields.

Ring Expansions of Oxiranes and Oxetanes

“…Professor Carreira has designed a clever anionic oxetane cascade using nitroalkyl nucleophiles (Scheme 40) [53]. Under mild reaction conditions, 3-oxetanones are converted into isoxazole products in one pot.…”

Silyl Glyoxylates. Conception and Realization of Flexible Conjunctive Reagents for Multicomponent Coupling

“…83, 84 Nitrile oxide-alkyne dipolar cycloadditions are the method of choice for the preparation of isoxazoles, but typically lead to the 3,5-disubstituted product with terminal alkynes. To prepare the needed constitutional isomer, we used the enolsilane 108 as the alkyne equivalent.…”

Rhodium(i)-catalyzed stereoselective [4+2] cycloaddition of oxetanols with alkynes through C(sp3)–C(sp3) bond cleavage

“…Encouraged by the considerable medicinal utility and unique molecular skeleton of oxetane and its derivatives, 8 we envisioned that they set a good stage for exploring new reactions. Herein, we report the highly efficient rhodium( i )-catalyzed cycloaddition of oxetanols with alkynes, via a tandem C(sp 3 )–C(sp 3 ) bond cleavage and subsequent cross addition over a 2-π unit for the first time, leading to complex dihydropyran ring systems.…”