Rearrangement Favorsky

An interesting variation of this theme starts with the a-chlorination of dicyclohexylketone (58). Treatment of the halo-genated intermediate with base leads to the acid, 60, by the Favorski rearrangement. Esterification of the acid with 2(1-pyrolidino)ethanol yields dihexyrevine (61). Both this agent and its earlier congener are recommended for use in GI spasms. 

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. 

A similar situation should prevail in the quasi-Favorski rearrangement. Indeed, it has been observed (65) that refluxing compounds 184 and 187 in xylene in the presence of sodium hydroxide gave the isomeric carboxylic acid derivatives 256 and J89 respectively. Thus, there is a neat inversion of configuration of the carbon atom which was initially bearing the halogen atom (cf. 185 and 188). 

The Favorski rearrangement normally goes with inversion at the terminus, as in 86 (semi-ezo-S) rather than 87 (semi-17). Reusch and Mattison (1967) have verified this for the pulegone oxides of which only one of the optically active forms is given in (181). It is of interest that the cyclopropanone intermediate opens abnormally, that is with retention. These authors note that their conditions are similar to those for electrophilic substitution with retention, namely frontside proton transfer from a polar aggregate (Cram, 1965). 

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] ... 

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). 

A skeletal rearrangement of a-hydroxyketones (103), similar to the known acid-catalysed acyloin transformation (Favorski, 1926), has been observed by Frearson and Brown (1968), who made efforts to distinguish between the possibilities of rearrangements taking place before and after ionization. These workers were of the opinion that an ion-rearrangement had been observed but the interpretation is open to question. 

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... 

Knutsson, L. Favorsky rearrangements. XVII. Studies on the mechanism of the rearrangement of 1,1,3-tribromoacetone using carbon-13-NMR spectroscx)py. Large intramolecular secondary deuterium isotope effect. Chem. Scr. 1972, 2, 227-229. 

Baudry, D., Begue, J. P., Charpentier-Morize, M. Favorsky-like rearrangement mechanism. Tetrahedron Lett. 1970, 2147-2150. 

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

A postulated intermediate in the Favorsky rearrangement is the product of dehydrochlorination. For rearrangement of 2-chlorocyclohexanone Goheen and Vaughan stirred a suspension of commercial sodium methoxide in 330 ml. of ether, added the... 

Breslow and co-workers used triethylamine to effect Favorski rearrangement of a.a -dibromodibenzyl ketone (1) to (2) and dehydrohalogenation of this intermediate to produce diphenylcyclopropenone (3). 

Favorski rearrangement, 1092, 1202 Fehling solution, 390 Fenton s reagent, see Hydrogen peroxide, with salt or oxide catalysts Ferric chloride, 297, 390-392, 702, 814 anhydrous, 392 Ferrocene, 181, 392 Ferrous chloride, 392 Ferrous sulfate, 393 Fieser reagent, 145 Fieser s solution, 222, 393, 737 Filter aid, see Celite Fischer indole synthesis, 899 Fischer reagent, see Karl Fischer reagent Fisetin, 64... 

An alternate synthesis was developed by E. Smissman and G. Hite2, using a modified Favorski rearrangement. Iso-nicotinic acid was methylated, reduced to 1-methyl-U-piperi-dinecarboxylic acid hydrochloride, and converted to the acid chloride hydrochloride. This was then condensed with benzene, chlorinated, treated with alkali, esterfied, and converted to the hydrochloride (See Figure 8). 

Steroidal spirocyclobutanones. The reaction of 17-halo-20-ketosteroids such as (1) with a 2.4-fold excess of dimethyloxosulfonium methylide results in formation of the cyclobutanones (3) and (4), formed presumably by way of a spiro-cyclopropanone (2) (Favorsky rearrangement).3... 

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