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Bond energy/eond order relationships for N-O linkages and a quantitative measur...
Johnstone, Robert A. W.; Loureiro, Rui M. S.; Labat, G.; Cristiano, Maria Lurdes SantosThe nitro group is active in metabolic systems and can be found as an integral part of a number of useful curative drugs and many toxic substances. The basis for much of this activity is not fully understood. It is not necessarily caused directly by through-bond electronic effects but may also be due to direct H-bonding to nitro or to indirect interference by the nitro group with existing H-bonding. An unusual ...
Investigations into the mechanism of action of nitrobenzene as a mild dehydroge...
Cristiano, Maria Lurdes Santos; Gago, David J. P.; Gonsalves, Antonio M. d'A. Rocha; Johnstone, Robert A. W.; McCarron, Moya; Varejão, Jorge M. T. B.Protonated nitrobenzene can be used to dehydrogenate a range of hydrocarbons, which already possess at least one double bond. Kinetic and spectroscopic results, together with known electrode potentials, yield approximate limits within which protonated nitrobenzenes can be expected to effect dehydrogenation of hydroaromatic compounds. A high yielding synthesis of benzo[ j ]fluoranthene is described.
Structural effects on sigmatropic shifts in heteroaromatic allyl ethersElectron...
Araújo, Nuna C.; Barroca, Pedro M. M.; Bickley, Jamie F.; Brigas, Amadeu F.; Cristiano, Maria Lurdes Santos; Johnstone, Robert A. W.In contrast to the known thermal, exclusively [3,3], O- to N- rearrangement of allyl groups in phenyltetrazoles (1, Scheme 1), the comparable migration of the allyl group in pseudosaccharyl ethers (3; Scheme 2) has been shown to proceed through both [1,3]- and [3,3]-mechanisms, 4, 5; for the pseudosaccharyl derivative of the natural product myrtenol (6; Scheme 3) only the product 7 of a [1,3]-shift has been obs...
The mechanism of formation of 8,8-dimethyl[4.2.1.0 3,7]nonan-6-yl acetate (fort...
Al-Qallaf, Fawzia A. H.; Fortes, A. Gil; Johnstone, Robert A. W.; Thompson, Ian; Whittaker, DavidAttempts to prepare 2-(2-hydroxyethyl)-6,6-dimethylbicyclo[3.1.1]hept-2-ene (nopol; 1) labelled with deuterium at C-10 by a process of oxidation of the primary alcohol group of nopol to the aldehyde, followed by H/D exchange and reduction back to alcohol, were unsuccessful because various oxidation procedures, including reaction with N-chlorosuccinimide at 278 8C, gave instead a carboxylic acid having an oxygen...
Thermal rearrangement of 3-allyloxy-1,2-benzisothiazole 1,1-dioxides: an unusua...
Cristiano, Maria Lurdes Santos; Brigas, Amadeu F.; Johnstone, Robert A. W.; Loureiro, Rui M. S.; Pena, Paula C. A.3-Allyloxy-1,2-benzisothiazole 1,1-dioxides isomerize thermally to give [3,3]- and [1,3]-products 6 of sigmatropic shift, of which the former reacts further to give solely the [1,3]-isomer.
3-( E )-But-2-enoxy-1,2-benzisothiazole 1,1-dioxide: unusual C—O—C ether bond l...
Barkley, J. V.; Cristiano, Maria Lurdes Santos; Johnstone, Robert A. W.; Loureiro, Rui M. S.Ethers such as the title compound, C~HIINO3S, (1), rearrange thermally to give N-allyl isomers, (2), in high yield. The X-ray structure determination of the title ether shows a central C--O--C linkage which has one very short (notional) C--O single bond and one exceptionally long single C--O bond. The thermal migration of allyl from the O to the N atom involves the breaking of one of the ether bonds in (1) and ...
Metal-assisted reactions. Part 25. Heterogeneous and homogeneous catalytic tran...
Cristiano, Maria Lurdes Santos; Johnstone, Robert A. W.; Price, Peter J.Transfer hydrogenolysis of 5-allyloxy- 1-phenyltetrazoles using either a heterogeneous or a homogeneous palladium catalyst and a hydrogen donor leads to cleavage of the allyloxy C-O bond to yield an alkane or an alkene and 1-phenyltetrazolone, depending on the catalyst used.
3-Hydroxy-2,6-dinitroacetophenone: an unusual substitution pattern resulting fr...
Cristiano, Maria Lurdes Santos; Johnstone, Robert A. W.; Pratt, M. J.Nitration of 3-hydroxyacetophenone gives 2,6-dinitro-3-hydroxyacetophenone, C8H6N206, in which the nitro groups have entered the sterically least favourable positions in the aromatic nucleus. None of the expected substitution in the 4-position was observed. The two nitro groups flanking the carbonyl side chain are different in that one is in the plane of the aryl ring but the other is twisted well out of the pl...
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