57765-59-0Relevant articles and documents
First synthesis, X-ray structure analysis and reactions of alkenyltriphenylbismuthonium salts
Matano, Yoshihiro,Yoshimune, Masanori,Azuma, Nagao,Suzuki, Hitomi
, p. 1971 - 1977 (2007/10/03)
Treatment of triphenylbismuth difluoride with alkenyltrimethylsilanes 1 or trimethylsilyl cyanidealkenyltrialkylstannanes 3 in the presence of boron trifluoride-diethyl ether gave the corresponding alkenyltriphenylbismuthonium tetrafluoroborates 2 in moderate to good yields. An X-ray crystallographic analysis of the salt 2e confirmed the distorted tetrahedral geometry of the central bismuth atom. When treated with a sulfinate 5 or the thiolate 11, the salts 2 readily transferred both the vinyl and phenyl moieties to these nucleophiles to afford the sulfones 7-10 or the sulfides 12, 13, respectively. In the presence of a palladium catalyst, the salt 2e underwent the Heck-type reaction with ethyl acrylate 17 to afford the dienoate 18 and cinnamate 19 in moderate yields. Action of KOBut on the salt 2b yielded p-tolylacetylene 22, while a similar reaction with the salt 2e in the presence of the styrenes 23 gave the cyclopropanes 24. A Hammett study of the latter reaction has suggested a possible involvement of an alkylidenecarbene as the intermediate in these base-promoted reactions.
Regioselectivity in the Addition of Singlet and Triplet Carbenes to 1,1-Dimethylallene. A Probe for Carbene Multiplicity
Creary, Xavier
, p. 1611 - 1618 (2007/10/02)
Singlet carbenes add preferentially to the more substituted bond of 1,1-dimethylallene (1), to give methylenecyclopropanes 3 as the major product.In contrast, many triplet carbenes add with differing regioselectivity, giving the thermodynamically preferre
Rearrangement of 2-Aryl-3,3-dimethylmethylenecyclopropanes. Substituent Effects on a Nonpolar Radical-Like Transition State
Creary, Xavier
, p. 280 - 284 (2007/10/02)
The effect of substituents on the thermal rearrangement of 2-aryl-3,3-dimethylmethylenecyclopropanes, 4, to 2-arylisopropylidenecyclopropanes, 5, has been determined.This has allowed an evaluation of substituent effects on a free-radical-like transition state devoid of polar character.In general, no correlation of all the data could be obtained with Hammett ? values.Electronegative meta substituents slightly decreased rates (ρ = -0.16).Conjugating substituents such as CN and CO2CH3 in the para position increased rates.The effect of the p-CF3 group was rate enhancing.The potential for C-F hyperconjugative stabilization is discussed as a radical-stabilizing feature.Thiomethyl and trimethylsilyl substituents in the para position increased rates.The possibility of radical-stabilizing interactions with vicinal ?* and ? orbitals is discussed. p-Methoxy substitution increased rates while p-fluoro substitution slowed rates.Resonance delocalization involving charge-separated forms 10a and 11 was suggested to be less favorable in the case of p-fluoro substitution.Delocalization involving an expanded octet accounted for increased rearrangement rates of p-Cl and p-Br-substituted 4.
