Applications of electron spin resonance spectroscopy to problems of structure and conformation. XIII. Formation of aliphatic semidiones under conditions of the acyloin condensation

Application of electron spin resonance spectroscopy to problems of structure and conformation. XXIX. Aliphatic semidiones. XXIX. Cycloheptane-1,2-semidione

“…The semifuraquinone 23 (0.90) was synthesized by electrolysis of the dichloro derivative in DMSO. Although in 12-19 H » ß , in 23 ß = 0.90 G » ay H = 0.19 G. This difference reflects the difference between a spin polarization mechanism (23) and a delocalization mechanism (12)(13)(14)(15)(16)(17)(18)(19). Another example of long-range hfs similar to H7 in 23 has been reported27 for 24 where H7 in the conformation shown lies in the nodal plane of the spin label.…”

“…Semidiones [12][13][14][15][16] provide further examples of 2-V and 2.5-V long range interactions by equatorial hydrogen atoms at the ß and positions in the basic skeleton of 9. There is no problem in assigning a consistent set of hfsc to 12-16 (Chart I).…”

“…(0.39) ( = 0.38 (6) G, Hd and H7) seen. The mechanism of the 2.5-V interaction of H7 in 8, 12-14, and [16][17][18][19][20] was investigated by changing the symmetry of the HOMO of the spin label. The semifuraquinone 23 (0.90) was synthesized by electrolysis of the dichloro derivative in DMSO.…”

Application of electron spin resonance spectroscopy to problems of structure and conformation. XXVIII. Aliphatic semidiones. XXVI. 1,4-Semidiones in C5-C7 carbocyclic systems

“….0 G 3.00 (1), 1.40 (2), 1.14 (2) G b. R = CH3, aH = 6.5 (3), 5.8 (1) Scch3h) but different symmetry properties for the MO containing the unpaired electron. 12 The benzo derivative of 7, i.e., 5, X = C(CH3)2 was prepared by electrolytic reduction of 2,2-dimethylindan-1,3-dione. The spectrum was a triplet of somewhat broad lines, a H = 2.65 G, which was further resolved by Nelsen9b to give a H = 0.10 (8).…”

Semidiones derived from bicyclic hydrocarbons

“…A large number of bicyclic semidiones have been obtained by this method and are discussed in the appropriate section of this thesis. A preliminary report of this work has been published (29).…”