Correspondence Cope rearrangement

The trans,trans- (184) and cis,trans-furanogermacrene (185a) derivatives and their corresponding Cope-rearrangement products, (186a) and (187),85 have been... 

The structures in the (1,0) and (0,1) comers are not necessarily stable species, they may correspond to hypothetical structures. In the Cope rearrangement it appears that the reaction only involves a single TS, independently of the number and nature of substituents. The reaction path may change from B A C depending on the system, but there are no intermediates along the reaction coordinate. 

Pd2(dba)3/l,4-bis(diphenylphosphino)butane (DPPB) in the presence of 2-mercaptobenzoic acid <95TL1267>. The Af-allylindolines can be easily oxidized to the corresponding indoles at room temperature with o-chloranil. Additionally, Al-allylanilines were also found to undergo aromatic 3-aza-Cope rearrangements in the presence of Zeolite catalysts to give indoline derivatives as the major product <96TL5281>. 

When there is a hydroxy substituent at C(3) of the diene system, the Cope rearrangement product is an enol that is subsequently converted to the corresponding... 

Isopolar activated complexes differ very little or not at all in charge separation or charge distribution from the corresponding initial reactants. These complexes are formed in pericyclic reactions such as Diels-Alder cydoadditions and the Cope rearrangement. 

According to the first process, acyclic alkyl nitronates (73) afford corresponding oximes and carbonyl compounds (3) (Eq.l). This process is similar to the well-known Cope rearrangement (Eq.l ) (233). 

Cyclopropanation of l,3-dienes. a,0-Unsaturated carbenes can undergo [4 + 2]cycloaddition with 1,3-dienes (12, 134), but they can also transfer the carbene ligand to an isolated double bond to form cyclopropanes. Exclusive cyclopropanation of a 1,3-diene is observed in the reaction of the a,(3-unsaturated chromium carbene 1 with the diene 2, which results in a frans-divinylcyclopropane (3) and a seven-membered silyl enol ether (4), which can be formed from 3 by a Cope rearrangement. However, the tungsten carbene corresponding to 1 undergoes exclusive [4 + 2]cycIoaddition with the diene 2. 

In addition to a-allenic a-amino acids, the corresponding allenic derivatives of y-aminobutyric acid (GABA) have also been synthesized as potential inhibitors of the pyridoxal phosphate-dependent enzyme GABA-aminotransferase (Scheme 18.49) [131,138-142]. The synthesis of y-allenyl-GABA (152) and its methylated derivatives was accomplished through Crabbe reaction [131], aza-Cope rearrangement [138] and lactam allenylation [139], whereas the fluoroallene 153 was prepared by SN2 -reduc-tion of a propargylic chloride [141]. 

The competition of the Cope rearrangement with cyclization processes was reported for perfluoro-l,5-hexadiene 457233. The cyclizations proceed undoubtedly via the corresponding diradicals 458 and 459 (equation 173). This course of events was revealed by using a... 

The dihydroxyoxepine moiety is a part of a fungal metabolite such as aranotin acetate exhibiting an antiviral activity. To prepare the 4,5-dihydroxyoxepines 546, the Cope rearrangement of the corresponding divinylepoxides 545 was used (equation 215)267-269. 

Aliphatic 3-aza-4-oxa-Cope rearrangement of ester-amide dienolates increases the synthetic utility of anionic [3,3]-sigmatropic rearrangement initiated by N—O bond cleavage. Treatment of the enehydroxylamine 94 with KHMDS in the presence of TMSCl at —80°C provided a mixture of iV,0-disilylated 95 and 0,0-disilylated 96 derivatives (equation 30). Both of these would, on [3,3]-sigmatropic rearrangement, provide the corresponding silyl ethers 97 and 98, from which 99 and 100 are obtained on workup. 

Saczewski and Debowski reported the l,4-diaza-3-oxa-Cope rearrangement of N-cyanate anilides (equation 52). Prototropic rearomatization of 176 and internal nucleophilic addition afford the corresponding benzimidazolinone 177, usually in moderate yields (32-78%). A concerted [3,3]-sigmatropic rearrangement is proposed based on the absence of para rearrangement product that usually results from homolysis or heterolysis of the N—O bond followed by recombination of the two radicals or ions. 

Whereas, cii-divinyl epoxides are reactive and well known to undergo thermal Cope rearrangement, the trans isomers are significantly more stable. White and co-worker (24) showed that thermolysis of divinyl epoxides such as 88 could generate the corresponding carbonyl ylide and that it could be intercepted by the addition of an activated acetylene to give the corresponding dihydrofuran 89, albeit in modest yield. 

Bicyclic acylcyclobutanes underwent rearrangement at 210 °C to give bicyclic dihydropyrans 2.120 At 150-180 °C a competing Cope rearrangement of the corresponding enol to give 1 predominated.120... 

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