C-S and C-N coupling reactions of barbituric acid via selective and complete bromination using greener KBr/H2O2 as a brominating agent

Department of Chemistry, Shri Mathuradas Mohota College of Science, Nagpur-440 009,

Maharashtra, India

E-mail: madhudash2001@yahoo.co.in Fax: 91-712-2744992

Department of Chemistry, R.T.M. Nagpur University, Nagpur-440 033, Maharashtra, India

Regional Forensic Science Laboratory, Govt. of Maharashtra, Amravati-444 603, Maharashtra, India

Taywade College, Koradi, Dist. Nagpur, Maharashtra, India

Manuscript received 05 March 2018, revised 16 March 2018, accepted 11 April 2018

1,3-Disubstituted/unsubstituted barbituric acids on treatment with KBr-H₂O₂ as a greener brominating reagent give mono and dibromo barbituric acids. With aqueous HCl selective bromination and without aqueous HCl complete bro­mination of active methylene group of barbituric acids took place. The reaction of monobarbituric acids with thiosemicarbazide and thioglyoxalic acid under refluxing in aqueous medium, simple C-S coupling products were ob­tained. The spiro C-N coupling product was obtained by the interaction of dibromo barbituric acid with thiosemicarbazide and C-N condensation product was obtained by the interaction of dibromo barbituric acid with guanidine nitrate, both reactions took place in aqueous medium under refluxing conditions. An environmentally benign, aqueous mediated C-S and C-N organic transformation by the interaction of barbituric acids mediated by KBr-H₂O₂ as a greener brominat­ing reagent is described. The simple product workup, use of inexpensive greener reagent KBr-H₂O₂ for bromination and simple purification without column are the additional advantages of synthetic protocol.