Beckmann rearrangements classical methods

The production of the intricate carbon framework of Lycopodine 407 by Grieco and Dai included an azepine formation by the classical Beckmann rearrangement method (equation 169). 

Other classical synthetic approaches to 2-furanamine have failed, including the Curtius method and Beckmann rearrangement of 2-benzoylfuran oxime. However, hydrazinolysis of AT-(2-furyl)phthalimide, obtained from phthalimide and 2,5-dimethoxy-2,5-dihy-drofuran, gives 2-furanamine which was not isolated but detected by GLC-MS and H NMR spectroscopy. The latter reveals the absence of imino tautomers (75AP713). The chemistry of 2-dialkylamino-5-phenylfurans is typical of enamines protonation occurs on carbon to produce iminium salts. They are stable to base but afford 5-phenylfuran-2(3//)-one on hydrolysis with dilute acid. 2-Morpholino-5-phenylfuran couples with diazonium salts and affords Diels-Alder adducts with maleic anhydride and IV-phenylmaleimide (73JCS(P1)2523). 

One of the classical reductive aldehyde syntheses is the Sonn-MUller reduction of imidoyl chlorides. The method is closely related to the Stephen reduction described in the previous section. As shown in Scheme 16, substrates (53) may be prepared either by the treatment of anilides with phosphorus pentachloride or sulfinyl chloride, or less usually via the Beckmann rearrangement. They are... 

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