7092-05-9Relevant academic research and scientific papers
Metallated Bicyclonona-2,6,8-trienes, Their Rearrangement to Barbaralanes, and a Short Synthesis of the Bicyclonona-2,6,8-trien-4-yl Anion
Bluemel, Janet,Koehler, Frank H.
, p. 1283 - 1290 (2007/10/02)
Five different anions are formed when bicyclonona-2,6,8-triene (1a) is deprotonated: the 6- and 7-yl anions when using tBuLi/TMEDA, the 4,6- and 4,7-diyl dianions when using nBuLi/tBuOK, and the 4-yl anion (1-) after quenching the dianions with THF.Reaction of the anions with Me3SnCl gives the 6-, 7-, and 4-monostannylated bicyclonona-2,6,8-trienes 1b, 1c, and 1d as well as the exo-4,7-, endo-4,6-, and endo-4,7-distannylated bicyclonona-2,6,8-trienes 1e, 1f, and 1g, respectively.Reaction of 1- with Me3SiCl and Me3PbCl leads to the corresponding 4-silyl derivative 1h and its plumbyl analogue 1i.Inversely, cleavage of 1d with MeLi allows to generate 1- under particularly mild conditions.The metallation of tricyclo2,4>nona-6,8-diene (3a), which was tested for an alternative route to 1-, gives two stannyl derivatives 3b and 3c which are substituted in the vinylic positions. - On heating 1d and 1i rearrange to yield 9-trimethylstannylbarbaralane (2d) and its plumbyl analogue 2i quantitatively.The reactivity decreases on passing from 1i to 1d whereas 1h does not react.Mercury and zinc derivatives of 1- are so labile that only dibarbaralylmercury (2j) and -zinc (2k) are observed by NMR spectroscopy.The title rearrangement proceeds by a 1,5-homodienyl metallatropic shift which involves an endo-type transition structure. - The new compounds 1b - i, 2d, 2i, 3b and 3c are characterized with emphasis on the NMR data including 1H, 13C, 119Sn, 207Pb signal shifts and various heteronuclear couplings.Key Words: Deprotonation / 1,5-Homodienyl shift / Bicyclonona-2,6,8-trienes / Tricyclo2,4>nona-6,8-dienes / Barbaralanes
(Z)- and (E)-1,2-Bis(phenylsulfonyl)ethylenes as Synthetic Equivalents to Acetylene as Dienophile
Lucchi, Ottorino De,Lucchini, Vittorio,Pasquato, Lucia,Modena, Giorgio
, p. 596 - 604 (2007/10/02)
A new method for introducing an ethylenic bridge via a cycloaddition reaction has been developed.It makes use of either (Z)- or (E)-1,2-bis(phenylsulfonyl)ethylene (5 or 6) as synthetic equivalents of acetylene.The high activation due to the two sulfonyl groups promotes cycloaddition even to very unreactive dienes.The removal of the two sulfonyl groups for the required formation of the carbon-carbon double bond is promoted by reduction with metal amalgams in high yields.These properties, associated with the stability of the reagents and the ease of performance of the reactions, make this method a very useful synthetic tool for the preparation of polycyclic dienes and a valid alternative to the commonly available reagents that largely depend upon oxidative methods.
cis-1,2-Bis(phenylsulfonyl)ethylene: a Novel, Convenient Acetylene Synthon in Diels-Alder Reactions
Lucchi, Ottorino De,Modena, Giorgio
, p. 914 - 915 (2007/10/02)
cis-1,2-Bis(phenylsulfonyl)ethylene (5) is found to be a reactive acetylene synthon in Diels-Alder reactions since, after cycloaddition to cyclopentadiene, cyclohexadiene, and cycloheptatriene, and reduction with sodium amalgam, the corresponding bicyclodienes (6)-(8) are obtained in good yields.
The Photoaddition of Ethylenic Hydrocarbons to Benzene
Bryce-Smith, Derek,Foulger, Brian,Forrester, John,Gilbert, Andrew,Orger, Brian H.,et al.
, p. 55 - 71 (2007/10/02)
The photoreactions of a range of acyclic and cyclic ethylenic hydrocarbons with benzene are described.The processes which occur depend on the ethylene, and in particular on its ionisation potential relative to that benzene, but in general, meta-cycloadditions occur in every case and often predominate. ortho-Cycloaddition tends mostly to occur with the ethylenes of lowest ionisation potential relative to that of benzene, and para-cycloaddition occurs with cyclobutene to a significant extent, but not with cyclopropene or cyclopentene.Acyclic ethylenes containing the group Me2C= also undergo ene-type acyclic para-addition to benzene to give cyclohexa-1,4-dienes.The ortho-, meta-, and para-cycloadditions are stereospecific with respect to the ethylene, but the ene-addition is non-stereospecific.The former are mostly insensitive to solvent polarity, the exception being ortho-cycloaddition of 2,3-dimethylbut-2-ene which is definitely promoted by polar solvents.The ene-addition of 2,3-dimethylbut-2-ene was promoted by methanol but not by acetonitrile: the use of CH3OD led non-stereospecifically to incorporation of deuterium in the 4-position of the adduct.Cyclohexene was anomalous in giving mainly a mixture of three cyclobutane dimers, with only minor proportions of the endo and exo, meta-adducts and possibly a trace of the para-cycloadduct.The photocyclisation of benzene to give a range of essentially saturated polymers up to ca. (C6H6)24 can be initiated by traces of cis-cyclo-octene.All the products, with the exception of the cyclobutane dimers from cyclohexene, are considered to be formed via S1 benzene, although T1 benzene-sensitised cis-trans isomerisation of the ethylenes also slowly occurs: Thus prolonged irradiation of cis-cyclo-octene and benzene leads eventually to the formation of trans-cyclo-octene and the corresponding cycloadducts.The mechanisms of these processes are discussed with reference to orbital symmetry considerations, and the observed effects of polar solvents and proton donors.Only the meta-cycloadditions appear to occur by concerted processes involving either initial meta-bonding in S1 benzene or initial meta-cycloaddition of the ethylene to S1 benzene.The ortho- and para-cycloadditions are formally forbidden as concerted processes from S1 benzene plus S0 ethylene, and these are considered to involve intermediates having a degree of dipolar character.
