7237 (19) M. C. R. Symons, J. Phys. Chem., 71, 172 (1967). (20) A. Carrington and' A. D. McLachlan, "Introduction to Magnetic Resonance," Harper and Row, New York, N.Y., 1967. (21) w. G. Williams, R. J. Pritchett, and G. K. Fraenkel. J. Chem. Phys., 52, 5584 (1970). (22) 0. Hassel and C. Romming, Quart. Rev., Chem. SOC., 16, 1 (1972). (23) I. V. Nelson and R. T. Iwamoto, J. Electroanal. Chem.. 7, 218 (1964). (24) A. I. Popov and D. H. Geske, J. Amer. Chem. SOC., 80, 1340 (1958). (25) A. i. Popov and W. A. Deskin, J. Amer. Chem. SOC.,80,2976 (1958). (26) R. S. Mulliken and W. B. Person, "Molecular Complexes," Wiley-Interscience, New York, N.Y.. 1969.
for the (27) This type of mechanism was also suggested by Romans, et oxidation of tetramethylhydrazinewith iodine. (28) J. Kommandeur and F. R. Hall, J. Chem. Phys., 34, 129 (1961). (29) F. Gutmann and H. Keyzer, J. Chem. Phys., 46, 1969 (1967). (30) J. H. Lupinski, J. Phys. Chem., 67, 2725 (1963). (31) V. D. Pokhodenko, V. A. Khizhnyi, V. G. Koshechko, and 0. I. Shkrebtii, Lhkl. Akad. Nauk SSSR,210, 640 (1973); Dokl. Phys. Chem.. 210,437 (1973). (32) The possibility of a triple ion species Br-TMB+.Br- is not unlikely. (33) A. I. Popov, "Halogen Chemistry," Vol. 1, V. Gutman. Ed., Academic Press, New York, N.Y.. 1967.
Aliphatic Semidiones. XXV. Bicyclo[n. 2.llalkane-2,3-semidionesl Glen A. Russell,* George W. Holland,* Kuo-Yuan Chang, Robert G. K e ~ k eJohn ,~ Mattox, C. S. C. Chung, Kerry Stanley, Kirk Schmitt, R. Blankespoor, and Y. Kosugi Contribution from the Department of Chemistry, Iowa State University, Ames, Iowa 50010. Received May 16. 1974
Abstract: The esr spectra of a number of bicyclo[2.2.l]heptane-2,3-semidionesand bicyclo[3.2.l]octane-2,3-semidionesare reported, including tri- and tetracyclic derivatives. Assignments of hyperfine splitting constants have been made by studies of deuterium and alkyl derivatives. A number of long range transoid, coplanar interactions between protons and the electron spin are reported, discussed, and analyzed in terms of valence bond resonance structures. Extended Hiickel and/or INDO calculations are reported for bicyclo[2.2.1] heptane-2,3-semidione and several alkyl derivatives, the corresponding semifuraquinone, bicyclo[2.2. I]hept-5-ene-2,3-semidione,and the semifuraquinone derivative and exo- and endo- tricyclo[ 3.2.1 .02-4]octane-6,7-semidiones.
Esr hyperfine splittings (hfs) by hydrogen atoms separated from a center of spin density by three or four bonds have been reported for a few monocyclic species such as cyR-5exo 0' clobutyl, cyclopentyl, and cyclohexyl radical^,^ piperidine n i t r ~ x i d e , ~and , ~ cycl~heptanesemidione.~ Resolution of these long range hfs requires a frozen conformation for the 0monocyclic system. Rigid bicyclic structures are often rich la. unsubstituted i, R-7a = CD, in such long range h f ~ . Since ~ , ~ our original report of such (R unspecified = H) i, R-7s = CH, long range hfs in bicyclic 1,2-~emidiones,~.~ similar observak. R - 1 , 7 ~= CH, b, R-7a = D tions have been reported for other spin centers including 1. R-7 = CH, C, R-7s = D alkyl radica1s,l0-l2 n i t r o x i d e ~ , s~e~m. i~q~~ i n o n e s , ' ~semi,'~ m. R-1,7,7 = CH, d, R-5,6exo = D furaquinones,I7 dicyanoethylene radical anions,ls dimethyln, R-l,7s = CH,; R-7a = CD, e, R-7 = CH,O dialkylhydrazine radical cations,I9 and 1 , 4 - ~ e m i d i o n e s . I ~ - ~ ~ f, R-1,4 = D;R-7 = CH,O p. R-5,6exo = CH, The present results complement previous reports on long q. R-B,6endo = CH, 8. R-1 = CH, range splittings in 2,3-semidiones derived from bicycloh. R-7a = CH, [n.1 .O]alkane~,~ I bicyclo [ n. 1.1 ]alkanes,22 bicycle[ 2.2.21alScheme I k a n e ~ , ~bicycle[ ~ . ~ ~3.2.01 octane^,'.^,^^ bicyclo [ 3.2.21non a n e ~ , ~ bicyclo .~' [ 3.3.1 ] n o n a n e ~ ,bicyclo[ ~ 3.3.21decanes,25 and a variety of polycyclic derivatives of cyclobutanesemiB-, DMSO, dior~e.~~ Synthesis of Bicyclo[2.2.l]heptanesemidiones. Treatment 0 0 of bicyclo[2.2.l]heptan-2-onewith traces of oxygen in basic crude DMSO solution failed to yield the esr signal of the semidione although this technique can be applied to a wide variety of cyclohexanone ~ I e r i v a t i v e s . Reaction ~ ~ , ~ ~ of this ketone, and most other bicyclo[2.2.l]heptan-2-ones not containing a syn- 7 substituent with selenium dioxide, failed to yield significant amounts of the a-diketone although the 0 crude product from norcamphor did yield the esr signal of la when treated with the propiophenone enolate ion in
K
t
An in situ preparation of 3-hydroxy-2-norbornanone from norbornene oxide in DMSO containing a trace of boron trifluoride etherate (80°, 24 hr)29 yielded la when the DMSO solution was treated with potassium tert- butoxide (Scheme I), but this method gave mixtures of radicals
4
when applied to other substituted norbornenes. 3-Bromonorcamphor in basic DMSO also yielded l a but this method30 failed for 3-bromocamphor itself. Russell, et al.
/
Aliphatic Semidiones
7238 Table 1. Hyperfine Splitting Constants of Bicyclo[2.2.1]heptane-2,3-semidionein DMSO at 25", K + Gegenion a H (G)--Semidione Substituents C-1,4 C-5,Bendo C-5,6exo c-7s 7
lan lba IC"
Id" lec lfc
Id 1ha 1s ljd lkd 11c
lmd lnc 1P" 1qa
None
anti -7D
syti-7D exo,exo-S,6-Dz 7,7-dimethoxy 1,4-D2-7,7-dimethoxy 1-methyl urzri-7-methyl atlti-7-CDa syri-7-methyl 1,syrt-7-dimethyl 7,7-dimethyl 1,7,7-trimethyl 1 ,syr?-7-dimethyl-arzti-7-CDI exo,exo-5,6-dimethyl endo,endo-5,6-dimethyl
-
__-_ ______
p
2.49 2.50 2.50 2.50 1.96 0.3b 2.51 (1) 2.37 2.38 2.52 2.55 (1) 2.07 2.08 (1) 2 , 0 8 (1) 2.59 2.33
2.49 2.50 2.50 0 . 40b 2.50 2.51 2.51 2.37 2.38 2.52 2.55 2.90 3.01 3.01
