Oxy-Cope/ene/Claisen reaction

Scheme 10.27. Microwave-assisted domino oxy-Cope/Claisen/ene reaction...

Scheme 6.84 Tandem oxy-Cope/Claisen/ene reactions and related transformations.

SCHEME 5 Attempts of the oxy-Cope/Claisen/ene reaction with more substituted species. 

One of the problems encountered in the synthesis of polycyclic compounds is the stereoselective formation of quaternary carbon centers. Barriault and coworkers reported the development of domino oxy-Cope/Claisen/ene reaction of divinyl cyclohexanol 130 as an efficient method for the assembly of decalin system possessing contiguous quaternary centers such as 133 (Scheme 8.21) [54]. Heating of alcohol... 

SCHEME 8.21 Cascade of an oxy-Cope/Claisen/ene reaction for the construction of complex diterpene core structures by Barriault etal. [52,53],... 

Taking advantage of the predictability of the domino oxy-Cope/Claisen/ene reaction, the same group reported the highly diastereoselective synthesis of a carbocycle 140 from 139 in 59% yield in a single operation [53]. The latter was converted in a few steps to 141, which represents an advanced... 

Sauer ELO, Barriault L. Highly efficient transfer of chirality from macrocyclic conformation in the tandem Oxy-Cope/-Claisen/Ene reaction. J. Am. Chem. Soc. 2004 126(27) 8569-8575. 

In a series of publications over the past few years, the group of Barriault has reported on microwave-assisted tandem oxy-Cope/Claisen/ene and closely related reactions [175-178], These pericyclic transformations typically proceed in a highly stereoselective fashion and can be exploited for the synthesis of complex natural products possessing decalin skeletons, such as the abietane diterpene wiedamannic... 

Barriault developed a new pericyclic domino process for the synthesis of the bioactive diterpenoid vinigrol (4-262), which was isolated from Vtrgaria nigra [92]. The natural product possesses antihypertensive and anti-platelet-aggregating properties. 4-262 contains a unique tricyclo [4.4.4.04a8a]tetradecane framework, which could be obtained by a combination of an oxy-Cope, a Claisen and an ene reaction... 

A remarkable example is the combination of three pericyclic reactions for the synthesis of decalin frameworks with quaternary centers by a tandem oxy-Cope-ene-Claisen reaction shown in 163 [539] (Scheme 1.72). 

Allylation of the 2,3-Wittig products (167) leads to diallylic ethers (171) in which one of the allylic double bonds is part of a 1,5-diene system. These ethers undergo 3,3-oxy-Cope rearrangement to afford vinyl allyl ethers (170), which rearrange in situ by a 3,3-Claisen process to yield the ( )-dienals (169). Some typical results are summarized in Table 14. The cyclopentanols (175) were shown to arise from aldehydes (169) by an intramolecular thermal ene reaction. ... 

Similar processes have been designed and utilized extensively by Barriault and coworkers for efforts in natural product synthesis. An impressive example of this strategy was utilized for the synthesis of the neo-clerodane skeleton of teucrolivin A. Thermal rearrangement of 92 under microwave irradiation results in a tandem sequence featuring an oxy-Cope rearrangement, followed by the Claisen rearrangement and subsequent ene reaction to give 93. 

A computational and experimental study of the oxy-Cope rearrangement of aldol products has been reported (Scheme 22) and a diastereoselective oxy-Cope/ene/Claisen reaction for the synthesis of decalin frameworks possessing four contiguous stereogenic centres has been applied. The aza-Cope/Mannich reaction has been reviewed. ... 

The oxy-Cope rearrangement generally is in competition with the retro-ene elimination reaction (6.112). These processes are considered in more detail in section 6.6. On occasions the Claisen rearrangement is also susceptible to side reactions. The first of these, the ortho-ortho Claisen rearrangement, involves... 

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