Reductive reagents, Beckmann

Another synthetic route via the Beckmann rearrangement, which is promoted by organoaluminum reagent along with alkylation, involves a new stereoselective reduction of the imino group. The starting oxime sulfonate (228) was synthesized from cyclopentanone (226) in three steps Reaction of 226 with 1-undecene in the presence of silver oxide produced the a-undecylcyclopentanone (227) which on successive treatment with hydroxylamine and methanesulfonyl chlo-ride-triethylamine gave the mesylate (228). Treatment of the oxime mesylate... 

The reductive Beckmann rearrangement of oximes has been effected with several types of aluminum hydride reagents. Early examples exhibited only moderate regioselectivity, giving mixtures of primary amines and rearranged secondary amines. Recently, diisobutylaluminum hydride was reported to be most satisfactory for this type of transformation (equation 20). Here dichloromethane is the solvent of choice, and attempted use of ethereal solvents results in the formation of a mixture of primary and secondary amines. ... 

Other papers on thioxanthene derivatives deal with the methylation, on sulphur and sulphoxide-oxygen respectively, of thioxanthene and thio-xanthone sulphoxide, the Beckmann rearrangement of thioxanthone oxime, and the quantitative reduction of thioxanthene sulphoxide to thioxanthene with sodimn borohydride-cobalt chloride, a reagent which appears to be of fairly neral applicability. ... 

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