Indoles in multicomponent processes (MCPs).

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

Cyclic organic carbonates represent a relevant class of chemicals that can be prepared from CO2 by cycloaddition to epoxides. The application of efficient catalysts is crucial in allowing the cycloaddition reaction to proceed under very mild conditions of temperature, pressure, and CO2 concentration, thus resulting in a sustainable and carbon-balanced approach to CO2 conversion. This is particularly the case if impure waste CO2 could be employed as a feedstock. In this Review, we have critically analyzed the burgeoning literature on the cycloaddition of CO2 to epoxides with the aim to provide state-of-the-art knowledge on the catalysts that can convert CO2 to carbonates under ambient conditions. These have been systematically organized in families of compounds and critically scrutinized in terms of catalytic activity, availability and mechanistic features. Finally, we provide an overview on the catalytic systems able to function using diluted and impure CO2 as a feedstock.

Catalytic Strategies for the Cycloaddition of Pure, Diluted, and Waste CO2 to Epoxides under Ambient Conditions

3beta-Hydroxy-lup-20(29)-en-28-oic acid (betulinic acid) is a pentacyclic lupane-type triterpene that is widely distributed throughout the plant kingdom. A variety of biological activities have been ascribed to betulinic acid including anti-inflammatory and in vitro antimalarial effects. However, betulinic acid is most highly regarded for its anti-HIV-1 activity and specific cytotoxicity against a variety of tumor cell lines. Interest in developing even more potent anti-HIV agents based on betulinic acid has led to the discovery of a host of highly active derivatives exhibiting greater potencies and better therapeutic indices than some current clinical anti-HIV agents. While its mechanism of action has not been fully determined, it has been shown that some betulinic acid analogs disrupt viral fusion to the cell in a post-binding step through interaction with the viral glycoprotein gp41 whereas others disrupt assembly and budding of the HIV-1 virus. With regard to its anticancer properties, betulinic acid was previously reported to exhibit selective cytotoxicity against several melanoma-derived cell lines. However, more recent work has demonstrated that betulinic acid is cytotoxic against other non-melanoma (neuroectodermal and malignant brain tumor) human tumor varieties. Betulinic acid appears to function by means of inducing apoptosis in cells irrespective of their p53 status. Because of its selective cytotoxicity against tumor cells and favorable therapeutic index, even at doses up to 500 mg/kg body weight, betulinic acid is a very promising new chemotherapeutic agent for the treatment of HIV infection and cancer.

Chemistry, biological activity, and chemotherapeutic potential of betulinic acid for the prevention and treatment of cancer and HIV infection

Multicomponent reactions have gained significant importance as a tool for the synthesis of a wide variety of useful compounds, including pharmaceuticals. In this context, the multiple component approach is especially appealing in view of the fact that products are formed in a single step, and the diversity can be readily achieved simply by varying the reacting components. The eco-friendly, solvent-free multicomponent approach opens up numerous possibilities for conducting rapid organic synthesis and functional group transformations more efficiently. Additionally, there are distinct advantages of these solvent-free protocols since they provide reduction or elimination of solvents thereby preventing pollution in organic synthesis “at source”. The chemo-, regio- or stereoselective synthesis of high-value chemical entities and parallel synthesis to generate a library of small molecules will add to the growth of multicomponent solvent-free reactions in the near future. In this review we summarized the results reported mainly within the last 10 years. It is quite clear from the growing number of emerging publications in this field that the possibility to utilize multicomponent technology allows reaction conditions to be accessed that are very valuable for organic synthesis. Therefore, diversity oriented synthesis (DOS) is rapidly becoming one of the paradigms in the process of modern drug discovery. This has spurred research in those fields of chemical investigation that lead to the rapid assembly of not only molecular diversity, but also molecular complexity. As a consequence multi-component as well as domino or related reactions are witnessing a new spring.

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Recent developments in solvent-free multicomponent reactions: a perfect synergy for eco-compatible organic synthesis

An efficient synthesis of 3,4-dihydropyrimidin-2-ones catalyzed by NH2SO3H under ultrasound irradiation.

An efficient and convenient approach to the synthesisof 2-amino-3-cyano-4-aryl-7,7-dimethyl-5-oxo-4 H -5,6,7,8-tetra-hydrobenzo[ b ]pyran derivatives using hexadecyltrimethyl ammoni-um bromide (HTMAB) as the catalyst (10 mol%) is described. Thismethod provides several advantages such as neutral conditions,high yields and simple work-up procedure, in addition water waschosen as a green solvent. Key words: tetrahydrobenzo[ b ]pyran, hexadecyltrimethyl ammo-nium bromide, aqueous media With increasing environmental concerns, more and morechemists are devoted to the area of ‘green synthesis’which means the reagents, solvent and catalyst are en-vironmentally friendly. In modern organic chemical re-search, Wender defined the ‘ideal synthesis’ as one inwhich the target components are produced in one step, inquantitative yield from readily available and inexpensivestarting materials in resource-effective and environmen-tally acceptable process. 1 The one-pot multicomponentcondensations represent a possible instrument to performa near ideal synthesis because they possess one of theaforementioned qualities, namely the possibilities ofbuilding-up complex molecules with maximum simplicityand brevity.

Tong‐Shuang Li

Papers

An efficient synthesis of 3,4-dihydropyrimidin-2-ones catalyzed by NH2SO3H under ultrasound irradiation.

A Clean One-pot Synthesis of Tetrahydrobenzo(b)pyran Derivatives Catalyzed by Hexadecyltrimethyl Ammonium Bromide in Aqueous Media

An efficient and convenient procedure for the preparation of 1,1-diacetates from aldehydes catalyzed by H2NSO3H

Improved synthesis of chalcones under ultrasound irradiation.

Montmorillonite K-10 and KSF as remarkable acetylation catalysts