- An efficient oxidative lactonization of 1,4-diols catalyzed by Cp*Ru(PN) complexes
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An efficient oxidative lactonization of 1,4-diols in acetone is accomplished by the well-defined ruthenium catalyst, whose bifunctional nature underlies the high efficiency as well as unique chemo- and regioselectivity of the reaction which provides a rapid access to γ-butyrolactones including flavor lactones hinokinin, and muricatacin.
- Ito, Masato,Osaku, Akihide,Shiibashi, Akira,Ikariya, Takao
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p. 1821 - 1824
(2008/02/02)
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- TiO2-photocatalyzed reactions of some benzylic donors
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TiO2-photocatalyzed oxidation of toluene (1a), benzyltrimethylsilane (1b), and 4-methoxybenzyltrimethylsilane (1c) has been carried out in acetonitrile under oxygen, under nitrogen, and in the presence of electrophilic alkenes under various conditions (using Ag2SO 4 as electron acceptor, adding 2.5% H2O, changing solvent to CH2Cl2). Benzyl radicals, formed via electron transfer and fragmentation, are trapped. A good material balance is often obtained. The overall efficiency of the process depends on the donor Eox, on the rate of fragmentation of the radical cation, and on the acceptor present (Ag+ is an efficient oxidant, an electrophilic alkene a poor one, O2 is intermediate). With ring-unsubstituted benzyl derivatives 1a and 1b, oxidative fragmentation occurs mainly close to the catalyst surface. The benzyl radicals form at a high local concentration and give benzaldehyde under O2, bibenzyl under N2 and dibenzylated derivatives by attack on the alkenes (acrylonitrile, fumaronitrile, maleic acid). In this case, using CH2Cl2-O2 enhances the yield of benzaldehyde. With methoxylated 1c, however, the radical cation migrates into the solution before fragmentation and, therefore, the free benzyl radical is formed. This radical in part is oxidized to the cation, giving a considerable amount of benzylacetamide (or of the alcohol with water), and in part is trapped by the alkenes. The last reaction is less efficient in this case and yields monobenzyl derivatives.
- Cermenati, Laura,Fagnoni, Maurizio,Albini, Angelo
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p. 560 - 566
(2007/10/03)
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- ACYLCYANAMIDES: VERSATILE SYNTHETIC INTERMEDIATES
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An improved general procedure for the preparation of acylcyanamides is described.Preliminary experiments have demonstrated that acylcyanamides exibit a rich chemistry.For example, acylcyanamides are easily converted into highly reactive dianions which, in
- Belletire, J. L.
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p. 2063 - 2072
(2007/10/02)
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- OXIDATIVE COUPLING OF CARBOXYLIC ACID DIANIONS
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The conditions, scope, and stereochemical consequences of a versatile approach to succinic acid derivatives are described.
- Belletire, J. L.,Spletzer, E. G.,Pinhas, A. R.
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p. 5969 - 5972
(2007/10/02)
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- DIMETALATED TERTIARY SUCCINAMIDES. ALKYLATION AND ANNELATION REACTIONS
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The reactions of dimetalated succinamides 1 with a variety of electrophiles give 2,3-disubstituted adducts (2) with high diasterioselectivity and annelated products (6-9).
- Mahalanabis, K.K.,Mumtaz, M.,Snieckus, V.
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p. 3971 - 3974
(2007/10/02)
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