Hetero-Claisen rearrangements

Using this hetero-Claisen rearrangement, Saito and coworkers95 have recently shown that octadiene 144 can be converted to the rearranged product 145 with total retention of... 

Allyl amines, allyl thioethers, and allylferrocenylselenide react analogously with butatrienylidene complex 10 by initial addition to C3 and subsequent hetero-Cope or hetero-Claisen rearrangement (Scheme 3.23) [21, 42-45]. 

Scheme 3.23 Hetero-Cope (hetero-Claisen) rearrangement in vinylalkynyl ruthenium complexes formed by addition of heteroallyl compounds to C3 of complex 10.

Langlois and co-workers ° developed a stereoselective hetero-Claisen rearrangement of camphor-based oxazoline A -oxides 300, available from hydroxylami-noisobomeol 298 and orthoesters 299. The rearrangement, initiated by acylation of... 

Agelas nakamurai from Japan produced the sesquiterpene sulfone, agelasidine A (353), which possessed antispasmodic activity. The structure was deduced from spectral data [309]. A simple synthesis of agelasidine A (353) utilised a hetero-Claisen rearrangement [310]. A biomimetic synthesis of 353 was also reported [311] and another synthesis of agelasidine A (353) was carried out in three steps from famesol [312]. 

In this section, the aliphatic Cope and Claisen rearrangements, as depicted in the transformation of I to 2 in Scheme 2, are discussed, as well as variations of the latter (i.e.. Johnson-Claisen, Ireland-Claisen, Reformatsky Claisen, F.schenmoser-Claisen. Ficini Claisen, and hetero-Claisen rearrangements). When X is oxygen, replacement of Cl and C2 with an aromatic ring... 

The discovery in 1971 that allvl pentafluorophenyl ether (22a) rearranges in the vapor phase at 365 C to 4-allyl-2,3.4,5,6-pentafluorocyclohexa-2.5-dienone (24a)19 marked the beginning of intensive and fruitful studies into the Claisen and hetero-Claisen rearrangements of arenes and hetarenes, studies which have been reviewed concisely by the principal investigator of this chemistry. G.M. Brooke.2"... 

Aromatic Hetero-Claisen-Rearrange-ment E10b2, 237... 

Reactions of alkynyliodonium salts with multidentate nucleophiles can be employed for the synthesis of heterocyclic compounds. Recent examples include preparations of thiazoles, selenazoles, and 2-mercaptothiazoles by the treatment of alkynyliodonium mesylates or tosylates with thioamides, selenoamides, and ammonium dithiocarbamate (Scheme 62) [169-171]. A novel hetero-Claisen rearrangement of tricovalent iodine(III) intermediates was proposed to account for the 2,4-disubstitution pattern of the thiazoles [169]. 

Alkynyl( aryl) iodine (I II) compounds 89 can also be employed in hetero-Claisen rearrangements [151] after reaction with appropriate thioamides yielding thiazoles of type 90 in reasonable yields as shown in Scheme 38 [152]. Ring enlargement reactions of furan derivatives into pyranones by hypervalent iodine compounds were reported as well [153]. 

A surprising feature of these reactions is their apparent departure from the Michael-addition/o -elimination sequence, which is expected to lead, via alkylidenecarbenes 275, to a 2,5-disubstitution pattern in the products. This has been attributed to the initial formation of iodine(III)-sulfur(selenium) adducts 276 and their collapse by a hetero-Claisen rearrangement to the isomeric alkylidenecarbenes 277 (Scheme 78). In view... 

Hetero-Claisen rearrangement. The rearrangement of allylic trichloroacetimidates (8.35) to allylic trichloroacetamides (8.36) is an example of the hetero-Claisen rearrangement ... 

Another example of the hetero-Claisen rearrangement is the thermal and catalyzed [3,3]-sigmatropic rearrangement of allylic phosphorimidates (8.37) to phosphramidates (8.38), which are converted into alylic amines of diverse structure. 

Rearrangements with other heteroatoms X, e.g., X = N, S, are called hetero-Claisen rearrangements. Sometimes, the rearrangement of I, X = S or N, is also called a 3-thia- or 3-aza-Cope rearrangement, respectively. In polyhetero-Claisen rearrangements other positions in I... 

For a hetero-Claisen rearrangement of allyl xanthate in the synthesis of agelasidine A see ref 369. Two sequential allyl xanthate rearrangements are described in ref 370. 

An intermolecular cyclization approach to C3 asymmetric oxindoles has been devised by Smith and coworkers who paired chiral A-phenylnitrone nucleophiles with ketene electrophiles, e.g., intermolecular fusion of 54 and 55 [37]. As illustrated in Scheme 16, the oxindole skeleton 57 materialized in 87% ee following a proposed sequence of nitrone addition to the ketene, a hetero-Claisen rearrangement, imine hydrolysis and, finally, cyclization to generate the lactam linkage. As an extension of this methodology, (5)-3-allyl-3-phenyloxindole 57 was transformed into enantiopure 3-phenyl-hexahydropyrroloindole scaffold 58. 

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