Evidence for an Olefinic Intermediate in the Configurational Inversion Accompanying Hydrogenolysis of a 7-Oxanorbornyl Vicinal Dibromide
The endo,endo-2,3-dibromo-7-oxanorbornenosuccinimide (1) undergoes complete inversion upon hydrogenolysis of the bromine substituents to form (5) (Zn/Ag couple in THF) or (26) (H2, Pd/C).The highly reactive dienophile, N-methyl 7-oxanorbornadienomaleimide (3) is shown to be a transient intermediates in the Zn/Ag couple experiments by trapping with furan.Deuterium labelling experiments have been used to help elucidate the mechanism of these reactions.
1,3-dipolar cycloaddition reactions of N-methyl-substituted tricyclic imides
The [3+2]?cycloadditions of N-methyl derivatives of unsaturated imides with various nitrile oxides to yield new bridged isoxazoline derivatives with potential biological activity is described.
Goksu, Gokce,Ocal, Nuket
scheme or table
p. 256 - 261
(2012/05/04)
Reductive heck reactions of N-methyl-substituted tricyclic imides
The palladium-catalyzed hydroarylation of N-methyl-substituted tricyclic imides was studied in order to find a new stereoselective access to a series of new exoaryl(hetaryl)-substituted tricyclic N-methylimides.
Goksu, Gokce,Ocal, Nuket,Kaufmann, Dieter E.
scheme or table
p. 1302 - 1308
(2010/06/13)
Structural studies on cycloadducts of furan, 2-methoxyfuran, and 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide
(Chemical Equation Presented) The early stages of the retro-Diels-Alder reaction are clearly apparent in the structures of the cycloadducts formed between furan or 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide. The degree of lengthening of the C-C bonds that break in this reaction is clearly related to the known reactivity of these cycloadducts toward this reaction. In the structures of the cycloadducts 21 and 22 derived from 2-methoxyfuran, the early stages of an alternative fragmentation reaction are apparent, consistent with the reactivity of these compounds in solution.
Yit, Wooi Goh,Pool, Brett R.,White, Jonathan M.
p. 151 - 156
(2008/09/17)
Unusual Stability of N-Methylmaleimide Cycloadducts: Characterization of Isobenzofuran Retro-Diels-Alder Reactions
Many years ago Diels and Thiele noted the unusual stability of maleic anhydride cycloadducts and employed this feature in scavenging anthracene generated in a retro- reaction.N-methylmaleimide, although nearly identical to maleic anhydride in rates of Diels-Alder reactions, forms even more stable cycloadducts.The rate constants for the four reactions that characterize the furan/N-methylmaleimide system were measured under the conditions used by Lee and Herndon to study the furan/maleic anhydride system.Comparison of the two dienophiles indicates thatN-methylmaleimide adducts are ca. 3 kcal*mol-1 more stable than the corresponding exo- and endo-maleic anhydride adducts.Somewhat larger (ca. 4 +/- 0.5 kcal*mol-1) differences in stability were found for the cycloadducts of the much more reactive diene isobenzofuran.N-Methylmaleimide is used as a diene scavenger to obtain rate constants for retro-Diels-Alder reactions of isobenzofuran adducts with maleic anhydride and some substituted analogs.The rates of retro-Diels-Alder reactions of substituted N-methylmaleimide adducts were also determined by an alternative method.The substituents examined enhance the rates of exo retro-Diels-Alder reactions by factors of 15-40, while endo adduct retro-Diels-Alder rates are only slightly affected.Calculations were done at the MP2/6-31G*//HF/6-31G* level to compare the heats of hydrogenation of maleic anhydride and maleimide.The reduction of maleimide is calculated to be 2.5 kcal*mol-1 more exergonic, supporting the experimental observations.
Tobia, David,Harrison, Roy,Phillips, Brian,White, Thomas L.,DiMare, Marcello,Rickborn, Bruce
p. 6701 - 6706
(2007/10/02)
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