Intramolecular coupling electrochemical

ET-induced cycloadditions of polycyclic olefins and cycloreversions of cyclobutane species have been studied by ESR spectroscopy [266]. Upon chemical and electrochemical reduction, 2,2 -distyrylbiphenyl rearranges by intramolecular coupling into a bis-benzylic dihydrophenanthrene dianion (Scheme 1), which can be either protonated to a 9,10 -dibenzyl-9,10-dihydrophenanthrene or oxidatively coupled to a cyclobutane species. It is interesting to note that the intramolecular bond... 

Diastereoselective reaction of diimines with sodium in ether leads to the formation of macrocyclic ethers of the type (32 equation 67) and (33 equation 68) in modest yields, However, there are no reports of examples using the templating effect of low-valent transition metals, as used to good effect for intramolecular carbonyl couplings. Electrochemical reduction of imines has been used to produce a variety of bicyclic structures via cyclization-aromatization (equation 69) or transannular cyclization (equation 70). ... 

Electrochemical reduction of bis(imine) (49) in strongly acidic media affords a 30% yield of trans-perhydrodiazocine (36), apparently via intramolecular coupling of an intermediate biradical (Scheme 9) <91JOC3063>. 

The electrochemical intramolecular coupling of both nonphenolic and diphenolic tetrahydrobenzylisoquinolines to supply morphinandienones is now well established (see the two equations below). 

On the other hand, since oxime ethers were electrochemically more inert than ketones under the electroreduction conditions, the electroreductive intra- and inter-molecular coupling of ketones with oxime ethers proceeded via anion radicals in good yields (equations 5 and 6) °4i. Moreover, cobaloxime-mediated intramolecular radical addition onto oxime functions in the electrolysis media proceeded to afford the cyclized aminoethers (equation 7). ... 

Intramolecular anodic olefin coupling reactions involving allyl- (equation 18) and vinyl-silanes (equation 19) can lead to good yields of quaternary carbons with control of the relative stereochemistry19,20. This is the first example of an electrochemical reaction that makes use of a temporary silicon tether. 

It is known that electrochemical reduction of oximes in protic media occurs in two steps the N—O bond is first reduced to form an imine and the latter is then reduced to afford a primary amine1,29. Tallec has shown that the amine from oxime 33 can be trapped intramolecularly (equation 16)35. Interestingly, the SS diastereomer predominates the chiral pyrrolidine ring derivative serves to control the stereochemistry of formation of the new benzylic chiral center. Electrochemical reductive cross-coupling of O-methyl oximes with carbonyl compounds in isopropanol at a tin cathode affords adducts (equation 17) which can be reduced further to 2-amino alcohols36. In this fashion, menthone could... 

Finally, it is important to note (Section 5.3.6) that electrochemistry and UV-Vis absorption spectra of molecular dyads or triads based on metal polypyridines show that electronic interactions between the components of the systems discussed above are too small to influence ground-state behavior. Nevertheless, they are sufficient to allow for very fast intramolecular electron transfer when electronically excited. In fact electronic coupling of 0.002-0.005 eV would be quite enough, but hardly detectable electrochemically. Detailed studies of electrochemistry and spectroscopy of these supramolecular systems and their components are, nevertheless, essential for the understanding of the energetics of photoinduced intramolecular electron and energy transfer reactions. 

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