Peter Bamfield

Conversion of o-nitrothiophenols into o-aminobenzenesulphonic acids

The mechanism of conversion of o-nitrothiophenols into o-aminobenzenesulphonic acids in aqueous dioxane has been investigated with particular reference to evidence for the rate-determining formation of a cyclic intermediate. This intermediate is susceptible to interception by both external and internal nucleophilic functions, and the sulphonic acid is shown by isotope labelling experiments to take two oxygen atoms from H218O in the reaction mixture, under conditions in which neither starting materials nor products exchange with H218O. A tentative pathway is advanced.

Aminochlorobenzenesulphonic acids: Synthesis of the missing isomers and corrections to the literature

Abstract Unambiguous routes to five aminochlorobenzenesulphonic acids are described. Two of these isomers have not been described before and this work shows that the literature on the other three is confused. The 13 C-n.m.r. spectra of all ten isomers have been measured. The isomers have been used to identify the products from the sulphonation of 2-, 3- and 4-chloroaniline in which HPLC analysis has been invaluable.

Selective functionalisation. Part 11. Selective hydrogenation by a novel palladium salicylidene-ethylenediamine complex and the properties of derivatives of some square planar homogeneous hydrogenation catalysts

Analogues of two reported homogeneous hydrogenation catalysts based upon square planar palladium complexes have been prepared with a view to modifying the structures to permit the control of selectivity by micellar interactions. Derivatives of bisacetylacetonatopalladium(II) in which the diketone was alkylated at C-3 or C-5 were prepared but no useful catalytic activity was observed for the reduction of nitrobenzene to aniline in the presence of pyridine. Complexes were also prepared from bisacetylacetonatopalladium(II) with 4-substituted pyridines as ligands; 4-tridecylpyridine afforded an unstable complex but 4-decylaminopyridine afforded a stable complex with low catalytic activity. A series of salicylidene imine palladium(II) complexes was prepared. Contrary to previous reports, the well-known salicyclidene-ethylenediaminepalladium(II) complex was not a catalyst for homogeneous hydrogenation but a new oligomeric green heterogenous complex with selective hydrogenation properties was discovered. This green complex was selective for the hydrogenation of alkynes, especially terminal alkynes, and reduced few other functional groups (ArNO2, ArCHO). Many variations on this structure were investigated in an attempt to discover a soluble or crystalline analogue of the green complex but no complexes with improved properties were isolated.