Homogeneous catalysis. Production of allyl alkyl sulphides by palladium mediated allylation
作者:Pamela R. Auburn、John Whelan、B. Bosnich
DOI:10.1039/c39860000146
日期:——
The use of O-allyl S-alkyl dithiocarbonate substrates in palladiummediated catalytic allylation gives carbonyl sulphide and allylalkylsulphides with net retention of configuration and their use obviates the problems associated with sulphur nucleophiles in catalytic allylation.
Initiation of radical cyclisation reactions using dimanganese decacarbonyl. A flexible approach to preparing 5-membered rings
作者:Bruce C. Gilbert、Wilhelm Kalz、Chris I. Lindsay、P. Terry McGrail、Andrew F. Parsons、David T. E. Whittaker
DOI:10.1039/b000835o
日期:——
Photolysis of dimanganese decacarbonyl [Mn2(CO)10] using visible light produces the manganese pentacarbonyl radical [·Mn(CO)5] which reacts with organohalides to form carbon-centred radicals. Efficient halogen-atom abstraction occurs with allylic or benzylic halides or polyhalogenated precursors bearing a weak carbon–halogen bond. Steric interactions are also important and primary halides generally react much faster with ·Mn(CO)5 than secondary or tertiary halides. The carbon-centred radicals can undergo efficient dimerisation or, in the presence of an acceptor double bond, cyclisation to form 5-membered rings. Cyclisation of terminal alkenes leads to primary radicals, which can then react by iodine- or bromine-atom transfer or, on addition of propan-2-ol, hydrogen-atom transfer. Hydroxylamines can also be formed when cyclisation reactions are carried out in the presence of TEMPO. These high-yielding cyclisation–trapping reactions are initiated under mild reaction conditions and the manganese halide by-products [of type XMn(CO)5] can be easily separated from products by a simple DBU work-up procedure.