Oxy-Cope-Claisen

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

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... 

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

Table 14 Tandem Oxy-Cope-Claisen Rearrangements of l,5-Dien-3-ol Allylic Ethers...

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. 

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). 

The Cope, oxy-Cope, and anionic oxy-Cope rearrangements belong to the category of [3,3J-sigmatropic rearrangements. Since it is a concerted process, the arrow pushing here is only illustrative. Cf. Claisen rearrangement. 

C Anionic oxy-Cope rearrangement 4d Claisen rearrangement of allyl vinyl ethers... 

E)-(Carboxyvinyl)trimethylam-monium betaine, 67 Ethyl 3,3-diethoxyacrylate, 131 Potassium hydride, 257 aza-Claisen rearrangement L-Valinol, 341 Cope rearrangement Ferric chloride, 133 oxy-Cope rearrangement Potassium hydride, 257 Silver(I) trifluoromethanesulfonate, 274... 

S ily 1) ally lie ethers 234 readily undergo 2,3-Wittig rearrangement upon treatment with an amide base to give, after methylation, 235 (equation 192)37,343. Tandem Claisen-2,3-Wittig-oxy-Cope rearrangement has been observed when 236 is treated under similar... 

---