Synthetic Photochemistry. LX. One-pot Formation of Spirocyclic 3-Acetyl-2-hydroxy-2-cyclopentenone Derivatives from Methylenecycloalkanes and Methyl 2,4-Dioxopentanoate
of proto-photocycloadducts of methyl 2,4-dioxopentanoate to methylenecycloalkanes and -alkenes spontaneously caused retro-benzilic acid rearrangement in high yields. The results are utterly different from those of sterically-crowded acyclic alkenes, with which the rearrangement occurred by thermolysis as a minor process.
Scope, limitations and mechanistic aspects in the selective homogeneous palladium-catalyzed reduction of alkenes under transfer hydrogen conditions
作者:Jean Michel Brunel
DOI:10.1016/j.tet.2007.01.053
日期:2007.4
A new and efficient mild Pd/P(t-Bu)3 catalyst for selective reduction of various alkenes under transfer hydrogen conditions has been developed leading to the corresponding saturated derivatives in chemical yields varying from 65 to 98%. Mechanistic rationale of this reaction has been also demonstrated.
hexabromocyclopentadiene (1) with sodium methoxide in methanol-glyme provides 1,2,3,4-tetrabromo-5,5-dimethoxycyclopentadiene (6). The reactivity of this new diene in the Diels-Alder reaction has been determined with a number of dienophiles. The greater reactivity of ketal 6 towards maleicanhydride compared to cyclopentadiene suggests that 6 behaves as an electron-rich diene in the Diels-Alder reaction.
Rotational correlation times and radii of dithiazol-2-yl and dithiazolidin-2-yl free radicals
作者:Shirley A. Fairhurst、Roger S. Pilkington、Leslie H. Sutcliffe
DOI:10.1039/f19837900439
日期:——
2-dithiazolidin-2-yl radicals have been shown to be useful model compounds for detailed e.s.r. studies of rotational reorientation in liquid and frozen media. Consequently they are also potentially useful spin probes and spin labels. The e.s.r. powder spectra have been analysed and the resulting g and A tensors were used to calculate rotational diffusion correslation times, rotational energetics of activation
Comparative studies about the hydroamination of unactivatedalkenes and dienes catalyzed by either cationic gold(I) triphenyl phosphite complexes or silver salts were performed using sulfonamides, anilines and carbamates as nucleophiles. Gold-catalyzed reactions generally, need lower loadings than those carried out with silver salts. Simple alkenes react only with sulfonamides and weak aromatic amines