Cope rearrangement thermal

A 5-allyl-5-vinyl-substituted 1,3-dioxan-2-one was used for a Cope rearrangement. Thermal treatment of 197 at 120-150 °C gave 5-alkylidene-l,3-dioxan-2-one in 75% yield (Equation 68) <2001JOC4447>. 

A. Kitagawa, T. A frustrated Cope rearrangement thermal interconversion of... 

Cope rearrangement. Thermal isomerization of 1,5-dienes by 1 3,3 shift. 

The most intriguing hydrocarbon of this molecular formula is named buUvalene, which is found in the mixture of products of the reaction given above. G. SchrOder (1963, 1964, 1967) synthesized it by a thermal dimerization presumably via diradicais of cyciooctatetraene and the photolytical cleavage of a benzene molecule from this dimer. The carbon-carbon bonds of buUvalene fluctuate extremely fast by thermal Cope rearrangements. 101/3 = 1,209,6(X) different combinations of the carbon atoms are possible. 

The most important sigmatropic rearrangements from the synthetic point of view are the [3,3] processes involving carbon-carbon bonds. The thermal rearrangement of 1,5-dienes by [3,3] sigmatropy is called the Cope rearrangement. The reaction establishes equilibrium between the two 1,5-dienes and proceeds in the thermodynamically favored direction. The conversion of 24 to 25 provides an example ... 

Migration from nitrogen to carbon is observed also in aza-Cope rearrangement [76] Ring expansion occurs in thermal rearrangement of azindine denvauves [77] (equation 17)... 

The Claisen rearrangemenC is a thermal rearrangement of allyl aryl ethers and allyl vinyl ethers respectively. It may be regarded as the oxa-version of the closely related Cope rearrangement. Claisen has discovered this reaction first on allyl vinyl ethers 1, and then extended to the rearrangement of allyl aryl ethers 2 to yield o-allylphenols 3 ... 

King and Harding296 have reported an interesting Sulfo-Cope rearrangement, and have presented evidence for the formation of the unstable sulfene (142) during the gas or liquid phase thermal [3,3]sigmatropic rearrangement of allyl vinyl sulfone (equation 88). 

Finally, a nice combination of a light-induced Wolff reaction of a diazoketone (e. g., 5-108) with a thermal Cope rearrangement, a light-induced Norrish type I cleavage and a recombination was developed by Stoltz and coworkers (Scheme 5.22) [38]. Here, irradiation of 5-108 at 254 nm in a photoreactor afforded the bicy-... 

Cairns N, Harwood LM, Astles DP (1994) Tandem thermal claisen-cope rearrangements of coumarate derivatives. Total syntheses of the naturally occurring coumarins suberosin, demethylsuberosin, ostruthin, balsamiferone and gravelliferone. J Chem Soc Perkin Trans... 

It was demonstrated that treatment of nitronate Me02CH=N(0)0Me with HCI (246), as well as heating (298) affords oxime (104a) as a result of standard thermal decomposition of alkyl nitronates, which occurs via a Cope rearrangement (233) (Scheme 3.87). 

Much experimental and theoretical work has been performed with the two allenes 1,2,6-heptatriene (32) and 1,2,6,7-octatetraene (34). Thermal isomerization of 32 leads to 3-methylene-l,5-hexadiene (346), a process that at first sight looks like a typical Cope rearrangement. However, trapping experiments with either oxygen or sulfur dioxide have shown that at least half of the rearrangement passes through the diradical 345 (Scheme 5.52) [144],... 

It was shown74 that the folded conformation of bicyclic substrates is a prerequisite for isomerizations such as 177 - 178. Thus, vyw-9-vinyl triene 183, being in the open conformation, undergoes an unusual Cope rearrangement to give the intermediate 184 which starts a cascade of thermal isomerizations at 60-65 °C (equation 57) whereas the awft -9-vinyl epimer 185 rearranges into the indene derivative 186 at 110°C in benzene solution (equation 58)74. 

The Cope rearrangement mechanism can be also strongly affected by other substituents. Thus, the normal electrocyclic process in the thermal isomerization of divinyl aromatics has been suppressed relative to the thermolysis of l,2-bis(trifluorovinyl)naphthalene 438 (in benzene, at 193 °C, 24 h)231. Three major products 440-442 were isolated from the reaction mixture, but none of them was the expected product 439. Also formed in low... 

Interesting examples of a tandem Cope-Cope rearrangement are represented by the transformation of Cookson s diester 499, which proceeds thermally to afford its ring-degenerate isomer 500 (330-350 °C, as a melt) (equation 188)246, and by thermal isomerization of bicyclic triene 501 into hexahydro-1-vinylnaphthalene 502 upon heating in chlorobenzene at 220 °C for 20 h (equation 189)247. 

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