16216-91-4Relevant 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
Structural Fluxionality in the Tricyclo2,8>nona-3,6-dienyl and Bicyclonona-2,6,8-trienyl Radicals
Walton, John C.
, p. 2169 - 2176 (2007/10/02)
E.s.r observation of radicals derived from 9-bromtricyclo2,8>nona-3,6-diene, and related compounds, showed that they rearrange by β-scission to bicyclonona-2,6,8-trienyl radicals extremly rapidly; the latter radicals have hyperfine splittings similar to those of allyl radicals. 9-Deuterio- and 2-deuterio-9-bromotricyclo2,8>nona-3,6-diene were reduced with tributyltin hydride.The pattern of deuterium scrambling in the bicyclonona-2,6,8-triene and tricyclo2,8>nona-3,6-diene products showed that the intermediate radicals take part in a degenerate rearrangement sequence which makes them fully fluxional in three dimensions.The two radicals are in equilibrium at ca. 375 K, but the bicyclotrienyl species is more important by a factor of ca. 102.Neither the experimental results nor MNDO semiempirical calculations provided any evidence of additional thermodynamic stabilisation in the radical pair beyond that expected for allyl delocalisation.
Tricyclo2,8>nona-3,6-dienyl and bicyclonona-2,6,8-trienyl; A Fluxional Radical Pair
Walton, John C.
, p. 468 - 469 (2007/10/02)
Tricyclo2,8>nona-3,6-dienyl and bicyclonona-2,6,8-trienyl radicals form a pair which is rendered fluxional by a series of degenerate cyclopropylmethyl type rearrangements.
Bicyclo nonatrienyl-lithium and -potassium and their Degenerate Rearrangements studied by Multiple Labelling with 13C and 2H, 13C Nuclear Magnetic Resonance Spectroscopy, 13C-13C Coupling Constants, and Isotopic Perturbation
Jonsaell, Goeran,Ahlberg, Per
, p. 461 - 468 (2007/10/02)
Bicyclononatrienyl-potassium (8) and -lithium (9) in -1,2-dimethoxyethane have been investigated by 13C nuclear magnetic resonance spectroscopy.The absence of an observable isotopic perturbation effect on 13C chemical shifts indicates a symmetric structure of this (CH)91- anion in solution, rather than rapidly equilibrating unsymmetrical homoaromatic ions.One-bond 13C-13C coupling constants obtained from the -labelled ion (10), 1JC1C2 38, 1JC1C7 40.0, and 1JC2C3 62.5 Hz, were compared with those of the corresponding hydrocarbon bicyclonona-2,6,8-triene (11).The couplings indicate no significant structural change in the bridgehead region and support a symmetrical delocalized structure for the bicyclononatrienyl anion.It is proposed that the controversial stabilization of carbanions is not caused by delocalization and homoaromaticity but is rather due to a previously ignored important interaction with the metal ion.The observed scrambling of 13C labels in (8) and (9), from C(3) to C(6)-C(9) and subsequently to C(2), C(4) and C(1), C(5), is consistent with a degenerate rearrangement via the 9-barbaralyl anion.Further support for this mechanism was obtained from the scrambling of two 13C labels from C(3) and C(2), C(4) which is three times faster to C(6)-C(9) than to C(1), C(5) in ion (10).
