Allylic rearrangement with condensation

Reaction type 6B of Table 10-1 is allylic rearrangement with simultaneous condensation with another molecule. The reaction, which is catalyzed by prenyl-transferases,3073 occurs during the polymerization of polyprenyl compounds (Fig. 22-1,Eqs. 22-2,22-3). Experimental evidence favors a carbocation mechanism for all of these reactions.308 309 See Chapter 22. 

The reaction is very slow in acetic acid alone, and accelerated as acetate by the addition of bases [59]. These two isomers undergo Pd-catalysed allylic rearrangement with each other. 3-Acetoxy-l,7-octadiene (139) is converted to the allylic alcohol 157 and to the enone 158, which is used as a bisannulation reagent [60], Thus Michael addition of 158 to 2-methylcyclopentanedione (159) and aldol condensation give 160. The terminal alkene is oxidized using PdCl2/CuCl/02 to the methyl ketone 161. After reduction of the double bond in 161, aldol condensation affords the tricyclic system 162. 

Allylic rearrangement 527,712 with condensation 527 Allysine 429 Alpha-carbon plot 64 Alpha effect on reaction rates 590 Alpha helix See a Helix Alport disease 438 Alternan 175... 

Treatment of 2,4,6-triphenylpyrylium perchlorate with 3-benzo[i>]-thienylmethylmagnesium bromide affords the 4//-pyran (155),460 which undergoes allylic rearrangement in diethylene glycol in the presence of sodium to give the 2//-pyran (156).461 Under the same reaction conditions 156 is further converted by an intramolecular aldol condensation into 3-(2,4,6-triphenylphenyl)benzo[6]thiophene. 

In summary, it can be said that the Y-substituted allylphenols can be prepared by Oalkylation of the sodium salt of the phenol in benzene, and —they usually cannot be prepared by the Claisen rearrangement. The condensation of free phenols with allylic halides, allylic alcohols, and dienes may give allylphenols, but frequently yields other products. - 94... 

Among the most favorable features of the Carroll variant of the Claisen rearrangement are the relative ease of preparation of the parent system by condensation of allylic alcohols with acetoacetic estet or di-ketene and the defined configuration of the intermediately generated double bond. The Carroll rearrange-... 

An alternative route to y,5-unsaturated ketones is via the Carroll-Claisen rearrangement, which uses allylic esters of 3-keto acids (which exist mainly in the enol form) as substrates. These are readily prepared by condensation of allylic alcohols with acetoacetic esters or diketene. Following rearrangement, the intermediate keto acid undergoes in situ decarboxylation on heating. 

CARROLL Rearrangement of Allyl Acetoacetic Esters Thermal condensation of allyl alcohols with ethyl acetoacetate in the presence of a catalyst, with loss of C02 a one pot ester exchange-Claisen-lreland rearrangement with loss of C02 (see 1st edition). 

These amidines have been extensively applied to dehydrohalogenation in organic synthesis and in some cases DBU (1) is more effective than DBN (2) [5]. A double bond can be also introduced into organic molecules by elimination of sulfonate ester instead of the halogen atom (i.e. dehydrosulfonation in addition to dehydrohalogenation). Furthermore, these amidines can be applied to the Wittig reaction [6], aldol condensation [6], 1,3-allyl rearrangement [7] and epimerization of the (3-lactam skeleton (at Ce of the penicillic acid derivatives). Sterically hindered phenols (e.g. 2,6-di(ferf-butyl)-4-fluorophenol) are (9-acetylated with DBU (1), which is superior to sodium hydroxide in the synthesis [8]. 

Condensation of the sodium enolate of acetylacetone 194 with carbethoxy-cyclopropyltriphenyl tetrafluoborate 195 led in high yield to acetylcyclopen-tenyl ester 196 and thence to ketal aldehyde 197. The latter with m-methoxy-phenethyl magnesium chloride 198 yielded allylic alcohol 199, which on Claisen rearrangement with dimethylacetamide dimethylacetal afforded amide 200. Conversion to amine, amine oxide, and Cope elimination then led to the desired... 

The [3,3]-sigmatropic rearrangement of allylic alcohols after condensation with ethyl 3,3-diethoxyacrylate leads to regiospecific syntheses of substituted allyl malonates in good yields (Scheme... 

The Overman pyrrolidine synthesis is a tandem reaction, or cascade, used to generate acylpyrrolidine derivatives. This process begins with condensation of an allylic alcohol/ether-containing secondary homoallylic amine with an aldehyde, followed by an aza-Cope rearrangement and subsequent Mannich reaction. Commonly, this reaction is run in refluxing benzene with an acidic additive, such as c/-10-camphorsulfonic acid (CSA). 

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