Synthesis of some bicyclo[2.2.2]oct-5-en-2-ones and bicyclo[2.2.2]octan-2-ones. Rearrangements accompanying oxidative decarboxylation with lead tetraacetate

Abstract

. Can. J. Chem. 59,344 (1981). I-Methoxy-2-methyl-1,4-cyclohexadiene (3), 2-methoxy-I-methyl-1.3-cyclohexadiene (2), and 2-methoxy-1,5,5-trimethyl-1,3-cyclohexadiene (14) on heating with maleic anhydride give 1-methoxy-endo-7-methylbicyclo[2.2.2]oct-5-ene-syn-2,3-dicarboxylic acid anhydride (7) and its 6-methoxy-I-methyl(16a) and 6-methoxy-l,8,8-trimethyl(l6b) analogues, respectively. On hydrolysis 16a and 16b give the corresponding keto dicarboxylic acids, 18a and 18b, via keto anhydrides 17a and 17b. During the course of 13C nmr spectroscopic greatly favours the desired regiochemistry of the studies (1) and other work (2, 3) on bicyclo-Diels-Alder reaction in route C, alkyl substitution [2.2.2]oct-5-en-2-ones and bicyclo[2.2.2]octan-2-is rarely found to lead to regiospecific addition (6), ones we had occasion to synthesize several members and indeed it was observed (4) that the product of these series. We report this work here because we mixture from route A contained a small amount consider that it includes several features of intrinsic of 4-methylbicyclo[2.2.2]oct-5-en-2-one, the regiointerest.isomer of 1. We therefore thought it worthwhile to I-Methylbicyclo[2.~.2]oct-~-en-~-one and Related investigate an alternative route-for the preparationCompounds of the latter, and chose 1-methyl-2-methoxy-l,3-l-Methylbicyclo[2.2.2]oct-5-en-2-one (1) was hexadiene (2) as the dime component of a Dielsfirst obtained by routes A and B in Scheme 1 (4). In Alder reaction pathway to the desired producteach case 1 was formed as a component of a cornIt has been reported (7) that Birch reduction of plex mixture of products and it was isolated by 0-methylanisole gives a mixture of the 1,4-dienes 3 preparative gas-liquid c.,romatograp~y~ sub-and 4, which is converted on treatment with potassequently 1 was prepared in good yield by route c sium amide in liquid ammonia to a mixture of the in scheme 1 (5). ~l~h~~~h the uortho effect-1,3-dienes 2 and 5, in which the former is the major component; the structures of the conjugated dienes 'Present address: Raylo Chemicals, ~t d . ,8045 Argyll Road, were inferred from the Diels-Alder adducts that Edmonton, Alta., Canada T6C 4A9.they formed. However, although the Birch reduc-

A Comparison of Intrazeolite and Solution Singlet Oxygen Ene Reactions of Allylic Alcohols

“…1 H NMR (CDCl 3 ) δ 1.14 (d, J = 6.5 Hz, 3H), 1.28 (s, 3H), 4.02 (q, J = 6.5 Hz, 1H), region between 5.32 and 5.4 severe overlap between 11 and 12 , 5.92 (dd, J = 11, 17.7 Hz, 1H), 8.27 (bs, 1H). S*R*‐3‐hydroperoxy‐3‐methyl‐4‐penten‐2‐ol ( 12 ). 1 H NMR (CDCl 3 ) δ 1.14 (d, J = 6.6 Hz, 3H), 1.34 (s, 3H), 3.99 (q, J = 6.6 Hz, 1H), region between 5.32 and 5.4 severe overlap between 11 and 12 , 5.99 (dd, J = 11.2, 17.7 Hz, 1H), 8.35 (bs, 1H).…”

“…The allylic hydroperoxides were identified by reduction with triphenylphosphine to the diols followed by comparison to published proton and carbon NMR of these compounds. cis ‐3‐methylene‐1,2‐cyclohexandiol (16‐OH) , (10) trans ‐3‐methylene‐1,2‐cyclohexandiol (16‐OH) (10), cis ‐3‐methyl‐3‐cyclohexen‐1,2‐diol (18‐OH) (11), 3‐methyl‐2,3‐epoxy‐cyclohexanone ( 21 ) (12). Spectral data for the trans ‐1,2‐diol, trans ‐3‐methyl‐3‐cyclohexen‐1,2‐diol (19‐OH) is not available but it is tentatively assigned on the basis of comparison of 13 C NMR chemical shifts in the reaction mixture and comparison with those published for 18‐OH (11).…”

Explorations of Caffeic Acid Derivatives: Total Syntheses of Rufescenolide, Yunnaneic Acids C and D, and Studies toward Yunnaneic Acids A and B

“…However, to highlight the specificity of such an event, it is clearly substrate-dependent in that many other 1,2-diketones, including our own for the model yunnaneic acid core, do not undergo such facile dimerization when exposed to silica gel. Finally, in what is an example of a yunnaneic acid A-type dimerization, Yates and Langford showed that treatment of diketone 57 with 0.5 equiv of MeLi could afford 58 , which then reacted with the remaining 57 in solution to afford mixed dimer 59 in 21% yield. Thus, this precedent provided a conceptual underpinning for what we hoped to achieve for the heterodimerization needed in our case.…”