Synthesis of Thiazoles Catalyzed by Dichlorotriazine Attached to Graphene Oxide

Abstract

and ytterbium(III) triflate. Each of these procedures may have its own advantages but also suffer from such apparent drawbacks as prolonged reaction times, complicated workup, low yield, or hazardous reaction conditions. Recently, graphene oxide (GO) has attracted significant interest as a catalyst in organic synthesis. Graphene and GO have large specific surface areas, chemical stability and high surface-to-volume ratios. GO is an efficient platform for functionalized graphene platelets that can potentially confer mechanical, thermal and electronic properties. Both small molecules and polymers have been covalently attached to GO’s highly reactive oxygen functionalities, or non-covalently attached on the graphene surfaces, for potential utilization in polymer composites, sensors, paper-like materials, drug-delivery systems and photovoltaic applications. We have previously reported the use of crosslinked sulfonated polyacrylamide tethered to nanoFe3O4 as a catalyst for the synthesis of 1,3-thiazoles. 19 As a companion study, we now report an easy method for the synthesis of these compounds through a three-component reaction of carbon disulfide, phenacyl bromide or 4-methoxyphenacyl bromide and a primary amine, using graphene oxide dichlorotriazine (GO-DCT) as an efficient catalyst. The reaction is conducted under reflux in ethanol (Scheme 1). The process for the preparation of graphene oxide dichlorotriazine (GO-DCT) catalyst is shown in Scheme 2. Graphene oxide nanosheets (GO) were prepared by modified Hummer’s method, and subsequently functionalized with dichlorotriazine (see Experimental section). We used the reaction of carbon disulfide, phenacyl bromide and benzyl amine on 1mmol scale as a model reaction and carried it out in the presence of CAN, NaHSO4, NiCl2, ZrOCl2, p-TSA, CuI and GO-DCT. We found that the reaction gave useful results in the presence of GO-DCT (2mg) under reflux conditions (Table 1). The best results were exemplified in Entry 12, with 92% yield. Further to this, we also reacted