62017-16-7Relevant articles and documents
New free-radical halogenations of alkanes, catalysed by N-hydroxyphthalimide. Polar and enthalpic effects on the chemo- and regioselectivity
Minisci, Francesco,Porta, Ombretta,Recupero, Francesco,Gambarotti, Cristian,Paganelli, Roberto,Pedulli, Gian Franco,Fontana, Francesca
, p. 1607 - 1609 (2007/10/03)
Reactions of alkanes with different halogenating systems are compared in order to explore the reactivity of phthalimido-N-oxyl radical in hydrogen abstraction; the importance of polar effects is emphasised.
Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
, p. 402 - 415 (2007/10/03)
Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
Dinucleotide and oligonucleotide analogues
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, (2008/06/13)
PCT No. PCT/GB97/00651 Sec. 371 Date Oct. 8, 1998 Sec. 102(e) Date Oct. 8, 1998 PCT Filed Nov. 3, 1997 PCT Pub. No. WO97/35869 PCT Pub. Date Oct. 2, 1997A compound which is a dinucleotide analogue of formula or a salt thereof, where B1 and B2 are each independently a monovalent nucleoside base radical, R1 is hydrogen or Y1, R2 and R3 are each independently hydrogen, halogen, hydroxy or -OY2, R4 is hydrogen, halogen, hydroxy, -OY3 or R7, R5 is hydrogen, halogen or R8, R6 is hydrogen, Y4 or a phosphoramidyl group, Z is a group of formula II, III or IV where R9 is hydrogen, halogen, hydroxy, -OY5 or R13, R10 is hydrogen, halogen or R14, R11 is hydroxy, R15 or -OR15 where R15 is a C1 to C10 aliphatic group, a C3 to C8 cycloaliphatic group, a C6 to C10 aromatic group or a C7 to C13 araliphatic group, and R12 is hydrogen, R12a or -OCOR12a where R12a is a C1 to C10 aliphatic group, a C3 to C8 cycloaliphatic group, a C6 to C10 aromatic group or a C7 to C13 araliphatic group, Y1, Y2, Y3, Y4 and Y5 are each indpendently a hydroxy-protecting group, and R7, R8, R13 and R14 are each independently a C1 to C10 aliphatic group, a C3 to C8 cycloaliphatic group, a C6 to C10 aromatic group or a C7 to C13 araliphatic group.
MECHANISMS OF FREE-RADICAL REACTIONS. XXIV. QUANTITATIVE DESCRIPTION OF THE POLAR EFFECTS OF SUBSTITUENTS ON THE KINETICS OF THE FREE-RADICAL CHLORINATION OF ALIPHATIC COMPOUNDS BY N-CHLOROPIPERIDINE
Dneprovskii, A. S.,Mil'tsov, S. A.,Arbuzov, P. V.
, p. 1826 - 1835 (2007/10/02)
The free-radical chlorination of 1-substituted alkanes with electron-withdrawing substituents by N-chloropiperidine in trifluoroacetic acid was studied by the method of competing reactions, and the relative rate constants were obtained for all positions of the substrates.The data on the position selectivity can be described satisfactorily by means of an electrostatic model of the polar effect of the substituent, calculated according to the Kirkwood-Westheimer equation.The obtained characteristics of the electrostatic effect can be successfully applied to calculation of the substrate selectivity and the intermolecular relative rate constants for all the positions, beginning with the third.The Taft equation is unsuitable for description of the effect of substituents on the reaction rate.
THE LONG-RANGE ACTION OF THE POLAR EFFECT OF SUBSTITUENTS ON THE ABSTRACTION OF HYDROGEN IN FREE-RADICAL CHLORINATION PROCESSES
Aver'yanov, V. A.,Ruban, S. G.,Klykova, M. B.,Golubev, V. E.
, p. 435 - 439 (2007/10/02)
The free-radical chlorination of 1-chloroalkanes between C3 and C6 at 263 deg K was studied under conditions with wide variation in the concentrations of the substrates in benzene.By analysis of the products from chlorination of the pure substrates it was shown that the deactivating effect of the polar substituent does not extend beyond the third carbon atom and is mainly determined by the inductive effect.In the transition to an aromatic solvent the deactivating effect on the substituent extends to the fourth carbon atom.The results are substantiated in terms of a contribution from dipole-dipole interaction between the substituent and the polar form of the transition state to the polar effect of the substituents.
MECHANISMS OF FREE-RADICAL REACTIONS. XIX. SELECTIVITY OF THE FREE-RADICAL CHLORINATION OF 1-CHLOROALKANES BY N-CHLOROPIPERIDINE
Dneprovskii, A. S.,Mil'tsov, S. A.
, p. 265 - 269 (2007/10/02)
The free-radical chlorination of 1-chloroalkanes ClH2l+1Cl (l = 4-7) by N-chloropiperidine was studied by the method of competing reactions, and the relative constants for all the positions of the investigated substrates were determined.The chlorination is a highly electrophilic process, and the effect of the substituents is transmitted through at least six C-C bonds.The results can be described satisfactorily by means of an electrostatic model of the polar effect of the substituents according to the Kirkwood-Westheimer equation.At the same time an attempt to describe the obtained data by means of the Taft equation led to unsatisfactory results.
