Hetero-Cope-rearrangement

Rearrangement ot 0-(2-pyrtdyi)oximes to 2-pyndones via a hetero-Cope rearrangement. 

Occasionally, addition products of 4//-l,2,4-triazole-3,5-diones or diazenedicarboxylic esters and oxepins have been obtained whose formation can be rationalized by an addition to the 2,4-diene system in the oxepin, e.g. formation of 10.190191 In these cases, the primary adduct usually cannot be isolated, because it undergoes a hetero-Cope rearrangement to a tricyclic or bicyclic structure in which the oxepin oxygen has become part of a carbonyl function.190 191,227... 

In a clever application of the hetero-Cope rearrangement, Martin used a Pd-catalyzed coupling of W-arylhydroxamates 362 with vinyl acetate to set up the [3,3] sigmatropic rearrangement 363 to 364 and final cyclization 364 to 365 [432-435]. Applications of this novel indole ring... 

The unstable cycloadducts 207, obtained from the dihydropyridines 205 (R = Me or Bn) and the benzoyl nitroso compound 206, undergo a hetero-Cope rearrangement in the presence of silicic acid to yield fused dioxazines 208 (equation 114)106. Adding the racemic hydroxamic acid 209 (R = r-Bu, cyclohexyl or Ph) to a two-phase mixture of... 

In principle, Cope-type rearrangements can occur in any 1,5-diene system consisting of six carbon and/or heteroatoms (equation 244). However, despite the apparent variety of potential possibilities, few examples of hetero-Cope rearrangements are known up to now. It should be noted that the structures depicted in equation 244 which can generally contain up to six heteroatoms are no longer real dienes. Nevertheless, we will briefly... 

Thiocamphor, under similar conditions, furnishes a vinylic disulphide as the major product (70%), which slowly undergoes a hetero-Cope rearrangement. ... 

Furthermore, the use of heteroatoms can lead to new functionalities on the rearrangement product. The hetero-Cope rearrangement has been reviewed ... 

Cope rearrangement 3-oxa-Cope or Claisen rearrangement 3-aza-Cope or 3-aza-Claisen rearrangement 3-aza-4-oxa-Cope rearrangement hetero-Cope rearrangement... 

Lantos and colleagues reported a different imidazole synthesis via hetero-Cope rearrangement. Oximes 116 reacted with benzenecarboxidoyl chloride affording adducts 117 that readily underwent a [3,3]-sigmatropic rearrangement at high temperatures (equation 35) to substituted imidazoles 118. 

Despite the typical use of the 1,5-dienic system in the hetero-Cope rearrangement the participation of triple bonds, C=N and C=C, in the [3,3]-sigmatropic rearrangement was also reported. Synthesis of A-substituted benzimidazolinones 175 by a hetero-Cope rearrangement of the adduct 174 formed by reaction of A-arylhydroxamic acids 172 with cyanogen bromide 173 in the presence of triethylamine and at low temperatures was reported by Almeida, Lobo and Prabhakar (equation 51). 

Similarly, the adducts of A -allylthiophenamines with DMAD lead to the formation of various tricyclic thiophene derivatives through hetero-Cope rearrangements. An analogous reaction of N-propynylaniline, on the other hand, leads to the formation of a pyrrole derivative (71) (Scheme 10). ... 

Sheradsky has found that the hydroxyl function of a ketoxime such as acetophenone oxime can be made to react with DMAD when the reaction is carried out in methanol with a basic catalyst, to give mixture of the fumarate and maleate isomers (164) in the ratio 2 1. This mixture on heating undergoes a hetero-Cope rearrangement followed by cyclization and dehydration to give dimethyl 5-phenylpyrrole-2,3-dicarboxylate (168) (Scheme 25). Similarly, Heindel and Chun have reported that vinyl ether adducts (171), obtained by the condensation of arylamide oximes with DMAD, get thermally converted into oxa-diazolines (172) or imidazolinones (174), depending on the reaction conditions. A similar reaction occurs with aromatic amidoxime-methyl propiolate adducts to give imidazoles (170) (Scheme 26). 1,2,4-Dioxazoles have been reported to be formed in the reaction of hydrox-amic acids with DMAD. - ... 

S.Blechert, Synthesis 1989, 71 -82 The Hetero-Cope Rearrangement in Organic Synthesis". 

Blediert, S. (1989) The hetero-Cope rearrangement in organic synthesis. Synthesis, 71—82. 

Of the many possible hetero-Claisen or hetero-Cope rearrangements, few have been applied to the synthesis of fluorine-containing compounds. 

Reaction of N-phenylhydroxamic acids (1) with vinyl acetate cat-suits in N-acylindoles (2) via a hetero-Cope rearrangement of an... 

In Table 1 these pericyclic processes are classified as hetero-Cope rearrangements according to Vogtle9. The position of the nitrogen atom and additional heteroatoms is assigned from the bond which will be broken by the [3,3] rearrangement. 

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