Sydnone: Synthesis, Reactivity and Biological Activities

What is it about?

Sydnones are among the most well-known mesoionic compounds. Since their synthesis in 1935 by Earl and Mecknay, numerous researches have shown that the chemical behavior, physical and biological properties of sydnones make them the most useful compounds in organic chemistry. Sydnones undergo thermal 1,3-dipolar cycloaddition reaction with dipolarophiles (alkynes or alkenes) to give exclusively derivatives containing a pyrazole moiety exhibiting numerous applications, such as pharmaceuticals and agro- chemicals. However, the sydnone cycloaddition reaction with alkynes requires harsh conditions, like high temperatures and long reaction times, giving poor regioselectivity to the resulting products. To overcome these constraints, new reactions named CuSAC (Copper-Catalyzed Sydnone-Alkyne Cycloaddition) and SPSAC (Strain-Promoted Sydnone-Alkyne Cycloaddition) have been developed, leading to pyrazoles with interesting constant kinetics.

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Why is it important?

Sydnones are still the most interesting and must-studied mesoionic systems. In fact, sydnone is a very important scaffold for the synthesis and development of peculiar heterocyclic derivatives with several applications in medicinal chemistry, material chemistry in catalysis and electrochemistry.

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