A novel one-pot approach to oxidative aromatization and bromination of pyrazolidin-3-one with HBr-H₂O₂system

Abstract

An efficient and green one-pot method for the oxidative aromatization and bromination of pyrazolidin-3-ones under mild conditions with a HBr-H2O2 system was developed. A mechanism was proposed.

Bromide Oxidation: A Safe Strategy for Electrophilic Brominations

“…[54] To avoid this, it can be beneficial to use an excess of bromide. Sometimes the oxidations can also be intentional, e. g. in the tandem oxidation/bromination of secondary alcohols 6 into α-bromoketones 7 (Scheme 3a) [50b] and of pyrazolidin-3-ones 8 into 4-bromopyrazol-3-ols 9 (Scheme 3b), [55] or in the oxidation/hydrolysis/bromination of phenylboronic acids 10 into brominated phenols 11 (Scheme 3c). [56]…”

Metal‐Free Iodine‐Promoted Oxidative Dehydrogenative Aromatization of Pyrazolidin‐3‐ones and Pyrazolines: An Efficient and Practical Approach to Functionalized Arylpyrazoles

“…Therefore, the efficient synthesis of these functionalized arylpyrazolols has attracted substantial attention from both academia and industry. To date, generally harsh reaction conditions, such as transition metal catalysts [5] or stoichiometric oxidant [6] (DDQ, MnO 2 or K 2 S 2 O 8 ) or highly corrosive acid (such as H 2 SO 4 or HBr) [6a–b] with restricted functional group tolerance are the most common methods used for the preparation of these compounds and their related biologically active derivatives [5–6] (Scheme 1a). Thus, the development of novel efficient and conventional protocol for the preparation of these scaffolds is exceedingly desirable.…”