Cyclononatetraenyl anion

Cyclononatetraenyl anion - 2852 Vol. 85 C OMMUNICATIONSHE E...

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2852 COMMUNICATIONS TO THE EDITOR Vol. 85 the antiperiplanar position, essentially as in the concerted E2 elimination. Thus, the difference between E2 and El in basic solvents may only be a matter of degree Hac /C H3 B / -pTs //,yHs H., - /c=c 'Solvent D\H H CHZ of polarization of the bond between the leaving group and the a-carbon. A41though it is not possible completely to rule out gegcnion free carbonium ions in each of the solvents, it is clear that they do not play a major role in these solvolytic eliminations. Streitwieser and Walsh' have demonstrated that the solvolytic displacement of tosylate by acetate group in the 2-octyl system occurs with 100% inversion in glacial acetic acid. .-I11 these resiilts are best accommodated by rejjection the idea that in these soholytic processes the fate of the carbonium ion is independent ifs origin. Acknowledgment.-This work was supported by the U. S. Xrmy Research Office (Durham). DEPARTMENT OF CHEMISTRY P. S. SKELL THE PENSSYLVASIA STATE LXIVERSITY M' L. HALL USIYERSITY PARK, PENNSYLVANIA RECEIVED JULY 3, 1963 17) A Streitwieser, Jr. . and T 11. Walih, Telrahedton Letters, 27 (1963). The Cyclononatetraenyl Anion Sir : The cyclononatetraenyl anion I should have a closed shell configuration of 10 T electrons and should be highly resonance stabilized. I That it should be aromatic is, however, questionable for two reasons: (1) The energy required to distort the angles of its bonds might be excessively large? and (2) the nine-membered ring might valence tautomerize3 spontaneously to form a single bond at the expense of a double Nevertheless, the cyclononatetraenyl anion does appear to be aromatic. Its synthesis is the subject of this report. Ia, hlT = Li+ IIa, S = C1 IIIa, S = Cl c,S=H c,X=H b,hlt = RC b, X = OCHa b, S = OCHs Cold chloroform reacts with dipotassium cyclo- octatetraenide4 in tetrahydrofuran (THF) to yield, after aqueous work-up, 9-chlorobicyclo [6.1 .O]nonatriene (IIa), b.p. 28-32' (0.2 mm.), in 327, yield; A:::" 218 mp (log E 3.57). *lnal. Calcd. for CsH9C1: C. ; H. j.94; C1, 23.23 Found: C, il.06; H, C1, 2,'3.42. Similarly, dichloromethyl methyl ether reacts to yield 9-methoxybicyclo [6.1 (IIb) in 267' yield; b.p. 54-56 (1.1 mm.); Xfl;:" 233 mp (log E 3.69). .Inal. Calcd. for CIoH110: C,Sl.O9; H,S.11. Found: C,80.80; H,8.18. SIeth- ylene chloride yields bicyclo [6.1 .0]nonatriene5 (IIc) in 4ijT; yield. IIa was identified by its ultraviolet spectrum and by its n.in.r. spectrum. The latter exhibited a multiplet 11 It- Huckel mulecular orbital delocalization energy is i3 5 3 (21 'The ccimpressiona! harrier i huwever, overcome by its next lower homolog. Lhr cyclr,,xtatetraenyI d nion IT. J Katz, W H Reinmuth, and D ith. J. Am ('hem Soc. 84, 02 i 19li2), and references therein] J. Katz. J Am (hem. .Sof , 83, :3781 (1900) Yogel. Au~em. C'hem , 73, A-IR (IOiil), and private c<,mmunicatim at 4.1 (rel. int. 6) and a coupled (J = 4 c.P.s.) triplet at 7.54 (rel. int. 1) and doublet a't 8.14 T (rel. int. 2). IIb exhibited a similar n.m.r. spectrum: a multiplet at 4.2 (rel. int. Ci), a singlet at 6.70 (rel. int. 3), and a coupled = 4 c.P.s.) triplet at 7.40 (rel. int. 1) and doublet at 8.40 T Only the anti isomers appear to be found, in striking contrast to the forma- tion of mixtures of comparable amounts of syn and
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Cyclononatetraenyl anion - 2852 Vol. 85 C OMMUNICATIONSHE E...

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