Aliphatic semidiones. XVI. Semidiones derived from the bicyclo[n.1.1.]alkanes

Abstract

Bicyclo[2.1.1]hexane-and bicyclo[3.1.1 ]heptane-2,3-semidiones have been examined by electron spin resonance spectroscopy in dimethyl sulfoxide solution. The long-range hyperfine splitting by the anti hydrogen atoms of the methano bridges decreases from 10 G in the hexane to 3.5 G in the heptane. Bicyclo[4.1.1 ]octane-3,4semidione was prepared and studied between -80 and +60°. Ring inversion was fast at all temperatures. A ring-expansion reaction of bicyclo[2.1.1 ]hexane-2,3-diones to bicyclo[3.1.1]heptane-2,3-diones by reaction with the methylsulfinylcarbanion has been detected.

Aliphatic semidiones. XXV. Bicyclo[n.2.1]alkane-2,3-semidiones

“…Similar structures have been previously invoked to explain the 2.5 V long range splitting in bicyclo[3.1.0]hexanes (20)21 and may be involved in the hfs by exo methyl groups at C-5.6 in lp (21). Hydrogen atoms at "C-9" in 16 have a fairly O-21 strong interaction and again a 2.5 V approximately coplanar transoid arrangement of bonds and orbital is possible (22) as is also the case for the anti-7 methyl group in lh,l,m (23) . This 2.5 V long range splitting which is pictured as functioning through the bonds {e.g., structures 19-23) is not reduced in magnitude by alkyl substitution at the syn positions if the geometry is not altered.…”

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

“…Semidiones Containing a Rigid C7 Chair Structure. A number of bicyclic and tricyclic derivatives of 9 have been prepared in the bicyclo[3.2.1]octane-6,7-semidione (12- (20)(21)(22)(23) families.…”

“…In 33, rapid conformational motion is observed even at -80°. 23 Semidione 34 undoubtedly exists with the sevenmembered ring in a boat conformation. Chart V" q ( , = 8.4, abH = 0.33 (2), ach =0.67 (2), adH = 0.33 (2) G)…”

Photochemistry of two .beta.,.beta.'-epoxy ketones, 3-oxatricyclo[3.2.1.02,4]octan-8-one and 3-oxatricyclo[3.3.1.02.4]nonan-9-one. Intramolecular reactions of .alpha.,.beta.-unsaturated aldehydo ketenes

“…This aliquot was also stored at 4 °C. After removal of solvent, the spectra of the aliquot and the main reaction mixture (230 mg crude; 20-25% material loss during photolysis) both revealed the same new product, trans-2methoxycyclohex-3-ene-l-carboxylic acid (7), formed from opening of the ß-lactone: IR 3500-2500 (s), 1710 (s, br), 1644 (w), 1095 (m, br) cm-1; NMR 1.43-2.83 (m), 3.30 (s, 3 ), 4.0 (m), 5.70 (s with fine structure, 2 H), 9.70 (br s, 1 H; variable).…”