The title products are unexpectedly acidic and they react spontaneously and in various ways with carbonyl compounds like ketones aldehydes, 1,3-diketones and α, β-unsaturated carbonyl compounds, they react in various ways with alkylating reagents. This review is a summary of research on the properties of the title compounds. It includes the structural features, both in solution and in the solid state. Aromatic aldehydes react with the title compounds to yield new type of cyclic betaines which were named ‘aldisates’. The spectral properties are discussed. The reaction with aliphatic ketones leads to the formation of isoxazolo-oxazine derivatives and the reaction with α, β-unsaturated aldehydes and ketones leads to polymers and Michael addition products respectively.