Ionones pinacol coupling reactions

In electrochemically initiated reactions coupling at the p-carbon to give 1,6-diones is preferred even 2,2,6,6-tetramethyl-4-hepten-3-one couples selectively via this mode. Pinacol formation is favored when -coupling is sterically hindered. Thus polyenones, such as retinal, are hydrodimerized to the corresponding pinacol in the presence of efficient hydrogen donors (equation 50). In the absence of added hydrogen donors the yield of retinal pinacol is much reduced, even though a- and p-ionone are efficiently coupled under these conditions (equation 51). ... 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

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