1911 Encyclopædia Britannica/Isoxazoles

ISOXAZOLES, monazole chemical compounds corresponding to furfurane, in which the ≡CH group adjacent to the oxygen atom is replaced by a nitrogen atom, and therefore they contain the ring system EB1911 Isoxazoles 1.jpg They may be prepared by the elimination of water from the monoximes of β-diketones, β-ketone aldehydes or oxymethylene ketones (L. Claisen, Ber., 1891, 24, p. 3906), the general reaction proceeding according to the equation

EB1911 Isoxazoles 2.jpg

W. Dunstan and T. S. Dymond (Jour. Chem. Soc., 1891, 49, p. 410) have also prepared isoxazoles by the action of alkalis on nitroparaffins, but have not been able to obtain the parent substance. Those isoxazoles in which the carbon atom adjacent to nitrogen is substituted are stable compounds, but if this is not the case, rearrangement of the molecule takes place and nitriles are formed. The isoxazoles are feebly basic.

The isoxazolones are the keto derivatives of the as yet unknown dihydroisoxazole, and are compounds of strongly acid nature, decomposing the carbonates of the alkaline earth metals and forming salts with metals and with ammonia. Their constitution is not yet definitely fixed and they may be regarded as derived from one of the three types

EB1911 Isoxazoles 3.jpg

By the action of nitrous acid on the oxime of o-aminobenzophenone as α-phenyl indoxazene, EB1911 Isoxazoles 4.jpg is obtained; this is a derivative of benzisoxazole.