Electroorganic Construction of Pyrazolidine-3,5-Diones

Abstract

Pyrazolidin-3,5-diones are an important motif in heterocyclic chemistry, which is highly interesting for pharmaceutical applications. One example is Phenylbutazone, an anti-rheumatic drug in human and veterinary medicine. Additionally, many pyrazolidin-3,5-dione derivatives are regularly tested on their pharmaceutical activity.[1] In classic heterocycle chemistry, the hydrazinic bond is established by ring closure using the corresponding hydrazine derivatives.[2] Most of them are toxic and require an upstream preparation due to low availability. Therefore, we now present a novel and sustainable synthetic approach to pyrazolidin-3,5-diones using electric current as oxidizing reagent. This electroorganic approach has some major advantages. Firstly, less or no reagent waste is produced.[3] Secondly, this transformation is an easy and elegant way to build the hydrazine moiety in pyrazolidin-3,5-diones. Thirdly, the required malonic acid diamides can be prepared in high yields from easy available starting materials.[4]