Mechanism of cyclization of aryl radicals containing unsaturated ortho-substituents
作者:Athelstan L. J. Beckwith、William B. Gara
DOI:10.1039/p29750000795
日期:——
Arylradicals generated by interaction of tributylstannane with aryl iodides containing unsaturatedortho-substituents cyclize regiospecifically to afford products containing the newly formed-radical centre exocyclic to the newly-formed ring. The relative rates of cyclization of a number of related radicals have been determined. The results are consistent with the hypothesis that the transition state
Benzyl vinylethers have selectively been arylated at either α or β position by fine-tuned Heck-type palladium catalyses. In contrast to previous protocols, no excess of arylating reagent or substrate chelation is necessary. For achieving good yields and high α/β-selectivities various factors determining the catalytic system had to be optimized. The results of DFT computational studies correlate selectivity
The conversion of 4-oxa-5-hexenyllithiums to 4-alken-1-ols: a novel [1,4]-wittig rearrangement
作者:William F. Bailey、Lyn M.J. Zarcone
DOI:10.1016/0040-4039(91)80002-n
日期:1991.1
corresponding 3-iodoalkyl vinyl ethers (1) by low-temperature lithium -iodine exchange, rearrange in high yield to 4-alken-1-ols (4) when warmed to room temperature. This transformation, which constitutes a [1,4]-Wittig rearrangement, is mediated by 5-exo-trig closure of 2 to a (2-tetrahydrofuranyl)methyllithium (3) followed by spontaneous ringopening to give 4.
Stable Arylpalladium Iodides and Reactive Arylpalladium Trifluoromethanesulfonates in the Intramolecular Heck Reaction
作者:John M. Brown、Jesus J. Perez-Torrente、Nathaniel W. Alcock、Howard J. Clase
DOI:10.1021/om00001a032
日期:1995.1
The reactions of 1-iodo-2-(3-butenyl)benzene and of two side-chain ether analogs with [1,1'-bis(diphenylphosphino)ferrocene](eta(2)-cyclooctatetraene)palladium gave the expected (eta(1)-aryl)-(eta(1)-iodo)palldium adducts, the 2-oxa-3-butenyl complex being characterized by X-ray crystallography. The alkene does not interact directly with palladium. Restricted rotation about the aryl-palladium bond was observed on the NMR time scale in all cases, since the methylene group(s) of the side chain were diastereotopic. The complexes were stable, but on treatment with silver trifluoromethanesulfonate in acetone at low temperature an unstable species was identified by H-1 and P-31 NMR in two of the three cases. Spectral observations were consistent with the formation and subsequent rearrangement of an intermediate along the pathway of an intramolecular Heck cyclisation with structure o-C6H4OC(CH3)(Pd[dppf]OTf).
TENNANT, SHAUN;WEGE, DIETER, J. CHEM. SOC. PERKIN TRANS. PT 1,(1989) N1, C. 2089-2093