An anomalous hydration/dehydration sequence for the mild generation of a nitrile oxide

Abstract

A nitrile oxide having a carbamoyl group is readily generated upon the treatment of 2-methyl-4-nitro-3-isoxazolin-5(2H)-one with water under mild reaction conditions, even in the absence of special reagents. The obtained nitrile oxide undergoes cycloaddition with dipolarophiles, alkynes 10 and alkenes, to afford the corresponding isoxazol(in)es, which are useful intermediates in the synthesis of polyfunctionalized compounds. A plausible mechanism underlying the formation of the nitrile oxide is proposed, which involves an anomalous hydration/dehydration sequence. DFT calculations were also performed to support this mechanism.

Metal‐Catalyzed Synthesis of Functionalized 1,2,4‐Oxadiazoles from Silyl Nitronates and Nitriles

“…In ac ompetition experiment 1.0 equiv.o fm esitylnitrile oxide (15) [16] and1 .0 equiv.o fs ilyl nitronate 4l were allowed to react with 1.0 equiv.o fn itrile 11j (Scheme 4). GC reactionm onitoring showedt hat both oxadiazoles 12k and 12l were formed in equal amounts, which indicates that both paths Aa nd Ba re possible.…”

Development of variously functionalized nitrile oxides

“…Nitrile oxide 2 undergoes cycloaddition reactions with alkenes [4–5], alkynes (Scheme 1) [4–5], nitriles [6], and 1,3-dicarbonyl compounds [7] to afford the corresponding polyfunctionalized heterocyclic compounds, which are not easily obtained by other approaches. Although this protocol is expected to be useful for synthesizing polyfunctionalized compounds, it is limited by the need of a N -methylcarbamoyl functional group.…”

1,3-Dipoles: Nitrile Imines, Nitrile Oxides and Nitrile Sulfides

“…The cycloaddition afforded functionalized isoxazoles and isoxazolines in good yields. 10 (G) The 1,3-dipolar cycloaddition of nitrile sulfides generated by microwave-assisted decarboxylation of 1,3,4-oxathiazol-2-ones has been investigated. …”