A New Nanomagnetic Cobalt Catalyst for Copper-free Sonogashira Coupling Reaction in Water at Room Temperature

Chitosan (CS), which is an N-deacetylated derivative of chitin, is an example of polysaccharidethat is widely spread in living organisms.Surprisingly, chitosan have unique characteristicsof the biomaterials; including the nontoxicity, biodegradability, environmentally friendly,renewability and abundance. More importantly, although, chitosan is a proper green and biodegradablecatalyst by itself, the presence of hydroxyl and amine groups in the chitosan structuremakes it possible to prepare the modified chitosan-based heterogeneous catalysts possessingnew properties. However, chitosan is only soluble in acidic aqueous media while it isinsoluble in basic aqueous medium, which is a necessary condition for cross coupling catalysis[1]. Carbon-carbon coupling reactions as a powerful synthetic tool and a major area inmultiple organic transformations have recently been one of the most intensively studied subjectsin organic synthesis which has been applied in various areas, including the synthesis ofnatural products, drugs and fine chemicals [2]. Nevertheless, these reactions suffer from problemsassociated with the separation and recovery of the homogeneous and costly Pd-basedcatalysts, which might result in undesirable metal contamination of the products. Therefore, tohave an efficient recovery and recycling of the catalyst, the immobilization of homogeneouscatalytic systems on different supporting materials has been the subject of intense researches.Recently, there has been an increased focus on palladium and copper free conditions in suchreactions. These problems can be largely overcome by using other transition metals such asnickel, copper, iron and cobalt. This metals are low cost, nontoxic and available. Sonogashirareaction employing heterogeneous cobalt-based catalysts have been reported less frequently[3]. In this work, we have successfully prepared an economical, environmentally benign andheterogeneous cobalt-based catalyst. This newly synthesized catalyst was characterized bydifferent methods such as XRD, SEM, FT-IR, TG and ICP analysis and used as an efficientheterogeneous catalyst in Sonogashira coupling reaction in water at room temperature (Fig.1).