Favorski type rearrangement

Oxidation of enamines.1 Oxidation of enamines of cyclic ketones in the presence of BFj etherate results in a Favorski type rearrangement to esters of contracted cycloalkanoic acids. A related reaction also occurs with enamines of aryl methyl ketones. 

Some deviations from this normal route which involves an oxirane intermediate occurred in sterically hindered ketones. For example, 2,2,6,6-tetramethyl-4-piper-idine underwent a-methoxylation (20%) [19], whereas cholestanone yielded a product of Favorski-type rearrangement [21], In 17-acetylated steroids the reaction with DIB-MeOH-KOH was normal but in 17-hydroxy-17-acetyl-steroids intramolecular cyclization occurred with formation of oxetanones [22] ... 

Favorski-type rearrangement Reaction of lead tetraacetate and BFj in benzene with the ketone (1) results in a mixture of a -acetoxylated ketones, 2a and 2b. If... 

Favorski-type rearrangement, 228-229 Ferric chloride, 185 Fetizon s reagent, 366 Fisher indole synthesis, 318, 322 Fluorenone, 431 Fluorodimethoxyborane, 186... 

An interesting synthesis of 4-epigibberellin Aj2 (86) from epicandicandiol (80) involves a Favorski-type rearrangement of the chloro-lactone (85). The A-ray analysis has been published of the 11-bromo-derivative of the nor-beyerane lactone (87). 

Normant et al.19), the migration power decreases in the order given underneath Eq. (15), and is reminiscent of that in other base-induced sextet rearrangements (benzilic acid, Favorsky-type). 

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