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      H 2O 2 in WERSA: an efficient green protocol for ipso-hydroxylation of aryl/heteroarylboronic acid

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          Abstract

          A mild, green, economic and efficient protocol has been developed for ipso-hydroxylation of aryl/heteroarylboronic acids to phenols using 30% aqueous H 2O 2 as an oxidant and WERSA (water extract of rice straw ashes) as a neat reaction medium.

          Abstract

          A mild, green, economic and efficient protocol has been developed for ipso-hydroxylation of aryl/heteroarylboronic acids to phenols using 30% aqueous H 2O 2 as an oxidant and WERSA (water extract of rice straw ashes) as a neat reaction medium. All reactions were carried out without using metal, ligand, activator or hazardous organic solvent with excellent yield within a very short reaction time at room temperature. Therefore, this appears to be the cleanest and greenest alternative protocol for ipso-hydroxylation of aryl/heteroarylboronic acids.

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          Most cited references24

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          Plant polyphenols: chemical properties, biological activities, and synthesis.

          Eating five servings of fruits and vegetables per day! This is what is highly recommended and heavily advertised nowadays to the general public to stay fit and healthy! Drinking green tea on a regular basis, eating chocolate from time to time, as well as savoring a couple of glasses of red wine per day have been claimed to increase life expectancy even further! Why? The answer is in fact still under scientific scrutiny, but a particular class of compounds naturally occurring in fruits and vegetables is considered to be crucial for the expression of such human health benefits: the polyphenols! What are these plant products really? What are their physicochemical properties? How do they express their biological activity? Are they really valuable for disease prevention? Can they be used to develop new pharmaceutical drugs? What recent progress has been made toward their preparation by organic synthesis? This Review gives answers from a chemical perspective, summarizes the state of the art, and highlights the most significant advances in the field of polyphenol research. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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            The antioxidant/anticancer potential of phenolic compounds isolated from olive oil.

            In our ongoing studies on the chemoprevention of cancer we have a particular interest in the health benefits of the Mediterranean diet, of which olive oil is a major component. Recent studies have shown that extravirgin olive oil contains an abundance of phenolic antioxidants including simple phenols (hydroxytyrosol, tyrosol), aldehydic secoiridoids, flavonoids and lignans (acetoxypinoresinol, pinoresinol). All of these phenolic substances are potent inhibitors of reactive oxygen species attack on, e.g. salicylic acid, 2-deoxyguanosine. Currently there is growing evidence that reactive oxygen species are involved in the aetiology of fat-related neoplasms such as cancer of the breast and colorectum. A plausible mechanism is a high intake of omega-6 polyunsaturated fatty acids which are especially prone to lipid peroxidation initiated and propagated by reactive oxygen species, leading to the formation (via alpha,beta-unsaturated aldehydes such as trans-4-hydroxy-2-nonenal) of highly pro-mutagenic exocyclic DNA adducts. Previous studies have shown that the colonic mucosa of cancer patients and those suffering from predisposing inflammatory conditions such as ulcerative colitis and Crohn's disease generates appreciably higher quantities of reactive oxygen species compared with normal tissue. We have extended these studies by developing accurate high performance liquid chromatography (HPLC) methods for the quantitation of reactive oxygen species generated by the faecal matrix. The data shows that the faecal matrix supports the generation of reactive oxygen species in abundance. As yet, there is a dearth of evidence linking this capacity to actual components of the diet which may influence the colorectal milieu. However, using the newly developed methodology we can demonstrate that the antioxidant phenolic compounds present in olive oil are potent inhibitors of free radical generation by the faecal matrix. This indicates that the study of the inter-relation between reactive oxygen species and dietary antioxidants is an area of great promise for elucidating mechanisms of colorectal carcinogenesis and possible future chemopreventive strategies.
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              The Chemistry of Phenols

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                Author and article information

                Journal
                RSCACL
                RSC Advances
                RSC Adv.
                Royal Society of Chemistry (RSC)
                2046-2069
                2015
                2015
                : 5
                : 124
                : 102723-102726
                Affiliations
                [1 ]Department of Chemistry
                [2 ]Dibrugarh University
                [3 ]Dibrugarh-786004
                [4 ]India
                Article
                10.1039/C5RA21354A
                4fd892aa-4b21-416c-b7b3-72bf5c0cebdb
                © 2015
                History

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