Hydrogen Peroxide-Mediated Rapid Room Temperature Metal-Free C(sp²)-H Thiocyanation of Amino Pyrazoles, Amino Uracils, and Enamines

Abstract

A rapid metal-and additive-free room temperature method for C(sp 2 )-H thiocyanation of aminopyrazoles, aminoisoxazole, aminoisothiazole, amino uracils, and aliphatic enamines has been developed in an aqueous medium using hydrogen peroxide as a benign oxidant and ammonium thiocyanate as a thiocyanating agent. On the other hand, the reaction of hydrogen peroxide and ammonium thiocyanate followed by one-pot addition of NaOH provides the corresponding disulfides in the case of amino azoles, and pyrimidine-fused 2-amino thiazoles were observed in the case of aminouracils. The salient features of this method are the use of an eco-friendly oxidant, reaction tunability to access different products, wide substrate scope, and good to very good yields.

Metal- and Solvent-Free Cascade Reaction for the Synthesis of Amino Pyrazole Thioether Derivatives

“…A yield of 74% (208.221 mg); a pale red solid; mp 72–74 °C; R f 0.51 (20% ethyl acetate in hexane); 1 H NMR (600 MHz, CDCl 3 ) δ 7.59 (2H, d, J = 6 Hz), 7.50–7.47 (2H, m), 7.36–7.34 (1H, m), 7.23 (2H, d, J = 6 Hz), 7.11–7.08 (3H, m), 4.20 (2H, s), 2.24 (3H, s); 13 C { 1 H} NMR (150 MHz, CDCl 3 ) δ 153.3, 148.7, 138.3, 138.2, 129.7, 129.0, 127.7, 125.2, 125.2, 123.5, 88.1, 12.3. The spectral data exactly match with the literature data …”

Electrooxidation Is a Promising Approach to Functionalization of Pyrazole-Type Compounds

“…The chemical approach has been actively developed over the past 10–15 years, but it is often associated with the use of an excess of unrecyclable oxidants, which can sometimes be toxic, scalding or poorly available (e.g., Br 2 [ 98 ], I 2 [ 99 ], DEAD [ 100 ], HIO 3 [ 101 ], H 5 IO 6 [ 102 ], I 2 O 5 [ 103 ], H 2 O 2 [ 102 , 104 , 105 , 106 , 107 ], K 2 S 2 O 8 [ 108 , 109 ], CAN [ 110 ], Mn(OAc) 3 [ 111 ], p -TSA [ 112 ], NCS [ 113 ], NBS [ 100 ], NIS [ 114 ], NTS [ 115 ], DDQ [ 116 , 117 ]). The electrochemical approach (see [ 22 ], Scheme 3 , route II b , and Scheme 13 ) is devoid of such disadvantages, but it is poorly studied in general [ 118 , 119 , 120 ].…”

Iodine/TBHP-Mediated One-Pot Multicomponent Protocol for Tandem C–N and C–S Bond Formation To Access Sulfenylimidazo[1,5-a]pyridines via C–H Functionalization

“…C–H sulfenylation with various sulfur reagents under transition metal-catalyzed and transition metal-free conditions has received considerable attention. Despite their use, multiple-step procedures are required to create these important moieties. − …”