Danupat Beukeaw,a Napassawan Rattanasupaponsak,a Tanakorn Kittikool,a

Kunita Phakdeeyothin,a Khampee Phomphrai,b and Sirilata Yotphan*,a

a Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Rama

VI Road, Bangkok 10400, Thailand

Phone number: +662-201-5154

Fax number: + 662-354-7151

E-mail: sirilata.yot@mahidol.ac.th

 

b Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of

Science and Technology (VISTEC), Wangchan, Rayong, 21210, Thailand.

 

Phosphorus–substituted heterocycles represent a vital class of organophosphorus compounds, which have constantly received attention from chemists in both academia and industry. The phosphorus substituents can alter the physical and chemical properties of compounds as well as regulate important biological functions. A number of these compounds are known to exhibit attractive prospects as pharmaceuticals, agrochemicals, and materials. Thus, considerable efforts have been devoted to explore highly efficient methods for preparation of such compounds. Among many synthetic methods available, direct oxidative coupling from parent heterocycles via metal-free cross-dehydrogenative coupling has become one of the atom economical synthetic strategies in modern synthetic chemistry, as it is simple, air-stable, and could bypass the necessity of prefunctionalization.

Herein, we report our finding on the direct phosphorylation approaches of the readily accessible pyrazolone substrates under metal-free conditions.Depending on the reagent employed and conditions (TBAI-TBHP or Selectfluor), phosphorus moiety is selectively installed at either N-2 or C-3 positions of pyrazol-5-one. These present metal-free protocols also feature convenient operations and simple reaction conditions, which could be useful for further derivatization of the related heterocycles to use in many applications.