¹³C magnetic resonance studies 133. An examination of the effect of conformation on β-enolization in some bicyclo[3.2.1]octan-2-ones

Abstract

. Can. J. Chem. 66, 454 (1988).To assess the influence of the conformation of the cyclohexanonc moiety in bicyclo[3.2.l]octan-2-ones on the reactivity for p-enolate rearrangement, the behavior of three derivatives under typical hon~oenolization conditions has been examined for comparison with 3.3-dimethylbicyc~o[3.2.l]octan-2-one (I), which was known to be snloothly converted to the [3.3.0] isomer 2. For this purpose, e1~do-3-tert-butyl-e,~o-3-methylbicyclo[3.2.l]octan-2-onc (8), elldo-9-tert-butyl-exo-9-methyl-exotricyclo[5.3.1 .0',6] undecan-8-one (9), and 9,9-dimethyl -elldo-tricyclo[5.3.1 .0',6] undecan-8-one (10) were prepared and treated with t-BuO-It-BuOH at 2 185OC for prolonged periods. Each is much less reactive than 1. The relative orientations of the carbonyl groups with respect to the sites for p-enolizhtion were determined by molecular mechanics (MM2) calculations. ' H /~H exchange in 9 and 10 was also examined under strongly basic conditions at 185OC. Dans le but d'Cvaluer I'influence de la conformation de la portion cyclohexanone des bicyclo[3.2.l]octanones-2 sur la rCactivitC conduisant a une transposition P-Cnolique, on a examin6 le comportement de trois dCrivCs dans des conditions d'homoCnolisation pour comparer avec le comportement de la dimCthyl-3,3 bicyclo[3.2.l]octanone-2 (I) qui se transforme facilement en son isomkre [3.3.0] (2). A ces fins, on a prCparC la tert-butyl-3-endo mCthyl-3-exo bicyclo[3.2. lloctanone (8), la tert-butyl-9-endo mCthyl-9-endo tricyclo[5.3.1.0'~6]und~canone-8-eso (9) et la dimCthyl-9,9 tricyclo[5.3

The structure, stereochemistry, and biosynthetic origin of a diterpenoid fungal metabolite, traversianal, established by 1H, 2H, and 13C magnetic resonance

“…Rather surprisingly, therefore, in tests that will be reported elsewhere, traversianal was found to be essentially inactive as a wilt or necrosis toxin towards a range of plants, although it does cause the efflux of betacyanins from 'part 135 of 13cmr studies; for Part 133 see ref. 25, for Part 134 see ref. 26. 2~ontribution No.…”

13C magnetic resonance studies. 138. An examination of the [3.2.2.0] → [4.2.1.0] rearrangement via β-enolization and H/D exchange in tricyclic ketones

“…The failure of 14 to rearrange was attributed to the difference in orientation of the carbonyl group caused by the conformational change of the six-membered ring. Additional support for this conclusion was subsequently provided by the results for some closely related systems (8). For 9, however, its relatively rigid skeleton would appear to render the orientation of the carbonyl group with respect to C-9, the expected p-enolization site, very similar to that in 1 and 4, but the relationship of the carbonyl group and C-3, the potential y-enolization site, will differ somewhat from that in 6.…”