Oximes, transformation into lactams

Ozonolysis of alkene 446 in the presence of acetaldehyde afforded diketone 448 through the intermediacy of 447. Ring expansion through Beckmann rearrangement took place when bis-oxime 449 was mesylated and warmed in aqueous tetrahydrofuran (THF). The bis-lactam so formed gave piperidinediol 450 on reduction with lithium aluminium hydride, and this compound was transformed into ( )-sparteine by treatment with triphenylphosphine, CCI4, and triethylamine (Scheme 105) <20050BC1557>. 

A convenient alternative to the Beckmann rearrangement is reported by Barton 1 Alkyl nitrones, readily available from the corresponding ketones, are smoothly transformed into A-alkylamides by treatment with toluene-/ -sulphonyl chloride, as shown in Scheme 36. Beckmann rearrangement of the oxime of (105) affords the isomeric lactam (106). This reaction is applicable also to saturated ketones. 

Mechanisms of the photo-Beckmann rearrangement have been advanced to involve the transformation of an excited singlet state of the oxime into an oxaziridine followed by the reorganization of the singlet excited intermediate to a lactam or amide. ... 

Ring transformation of the mannopyranoside derivative 61, obtained from noncarbohydrate, to 1 has been developed (Scheme 7).225.226 Radical cyclization of the thiocarbonylim-idazolo derivative of 61 gave 62, which upon oxidation and reduction afforded 63 (30%) and 64 (55%). The latter was benzylated to give 65, which was converted into (fi)-oxime 67 via 66. Beckmann rearrangement of 67 followed by desilylation furnished 68. Cyclization of 68 to indolizidine skeleton followed by debenzylation, reduction of the lactam with BMS and hydrolysis afforded (-)-swainsonine (1). 

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