Current Organocatalysis - Volume 4, Issue 2, 2017

Background: Since 1960s, vitamin B1 has been used as a catalyst in biochemical process and serves as a coenzyme for important types of transformations. The term “organocatalyst” is a concatenation of the words “organic” and “catalyst.” Vitamin B1 is an organocatalysis and structure of vitamin B1 contains a pyrimidine ring and a thiazole ring linked by a methylene bridge. Vitamin B1 is a nonflammable, water soluble, inexpensive, and non-toxic green organocatalyst. Methods: Nowadays focus of chemists are shifting towards finding catalysts that will enable industrial processes to be less polluting, to operate with better atom economy and produce purer products which last longer. Results: Vitamin B1 is used as a catalyst in the synthesis of various biological heterocyclic compounds and other reactions without using any toxic volatile and hazardous acid and basic catalyst. In most of the cases, good yield of desired products was obtained in short time using vitamin B1 as a catalyst. Conclusion: The present review highlights the catalytic potential of vitamin B1 as a catalyst in the construction of various biologically active heterocycles as well as other organic transformations that have been made in the last few decades. The high catalytic activity, its selectivity, recyclability, its superior chemical and thermal stability and ease of separation make it an attractive and a promising organocatalyst for future.

Peptides play crucial roles in the nature and execute almost all biochemical transformations in the form of proteins, enzymes, hormones, neurotransmitters and/or toxins. Just to mimic the effective properties of enzyme in bio-catalysis, we have to gain knowledge in structure of synthetic peptides and their role mainly in catalysis. Application of oligopeptides as catalysts in order to mimic the performance of enzymes is a particularly elegant approach to asymmetric chemical synthesis. The diversity of available amino acids (natural and synthetic), well established coupling techniques, and the ease of modification make peptides ideally suited for the design of potent catalysts. Recently, synthetic peptides have proven to be useful catalysts for a number of fundamental organic transformations such as bromination, sulphonylation, phosphorylation, acylation, C-C cross coupling, aldol condensation, epoxidation, oxidation of alcohol, and asymmetric induction. This review highlights the application of peptides as potential catalysts for diverse organic synthesis and potential role in the asymmetric chemical modifications.

Urea and its derivatives, which are usually generated through the carbonylation reaction between amines and carbonylation reagent, have been found widespread applications in agriculture and pharmaceuticals. Among the carbonylation reaction, it is the most appealing and promising strategy that employs CO2 as a green carbonylation reagent. However, CO2 inherent thermodynamic stability and kinetic inertness limit its application. Apart from being regarded as one of the green solvents, ionic liquid is also an efficient organocatalyst for CO2 capture or activation due to the interaction between CO2 with cation or anion of ionic liquid. In this mini-review, we have summarized representative synthetic methodologies of urea derivatives using carbon dioxide as a green carbonylation reagent and using ionic liquids as solvents and/or organocatalysts.

Background: Due to significant biological activity associated with N-, O- and Sheterocycles, a number of reports for their synthesis have appeared in recent decades. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. This review summarizes the applications of gold catalysts with emphasis of their synthetic applications for nitrogen containing five-membered heterocylces. Objective: The transition metal catalyzed protocols have attracted the attention as compared to other synthetic methodologies because they use easily available substrates to build multiply substituted complicated molecules directly under mild conditions. In organic synthesis one of the most powerful and useful protocols are constituted by transition metal catalyzed coupling transformations. The N-heterocycles are synthesized by this convenient and useful tool. Conclusion: The efficient and chemoselective synthesis of heterocycles by this technique has appeared as an important tool. This review shows a highly dynamic research field and the employment of gold catalysts in organic synthesis. Several strategies have been pointed out in the past few years, to meet more sustainable, efficient and environmentally benign chemical products and procedures. The catalytic strategies have been focus of intense research because they avoid the use of toxic reagents. Among these catalytic strategies, highly rewarding and an important method in heterocycles synthesis is metal catalyzed synthesis.

Background: L-proline as a famous and most applied organocatalyst contains a nucleophilic secondary amino group and a carboxylic acid moiety functioning as a Brønsted acid has been used to catalyze more and more essential transformations. Although the L-proline is commercially available at low cost, however the organocatalytic methods in general require high catalyst loading for the achievement of high conversions in reasonable reaction times. In this research work, L-prolinate- Amberlite is introduced as an efficient and reusable organocatalyst for the one-pot synthesis of biscoumarins. Methods: L-prolinate catalyst was supported on the surface of commercially available amberlite IRA- 900OH (mesh 16-50) using ion-pair immobilization. Results: Preparation of the heterogeneous polymer-supported L-prolinate catalyst by this procedure is facile and straightforward. The reaction times for the preparation of biscoumarin derivatives using [Amb] L-prolinate adduct are shorter than reported methods. The introduced catalyst is cheap, easy to handle, shorter reaction times and the catalyst does not have any corrosion property. More importantly, its bifunctional activity can efficiently catalyze this ring opening reaction by simultaneous activation of both electrophilic and nucleophilic sites during the reaction progress. Conclusion: This methodology made the organocatalyst mobile and flexible. This condition not only helped the supported catalyst to be more efficient than its non-supported form, but also made it to be easily recoverable with simple filtration. The catalyst can be used at least eight times without substantial reduction in its catalytic activity and very low leaching amount of organocatalyst into the reaction mixture was observed.