Science of Synthesis

Chataigner, I.; Harrison-Marchand, A.; Maddaluno, J., Science of Synthesis, (2005) 26, 1174.

An example of the synthesis of a 3-oxo ester by a [3,3]-sigmatropic rearrangement involving an allylic and vinylic ether was described in Ludwig Claisen's original paper on what has since become known as the Claisen rearrangement.[‌454‌] An intramolecular mechanism has been proposed for the thermal rearrangement of 3-(alk-2-enyl)oxybut-2-enoates into 2-alkenyl-3-oxobutanoates via a cyclic transition state.[‌455‌] Alkylidenetetrahydro­furans (e.g., ‌149‌) rearrange either into cycloheptanones, with allyl inversion (under thermal conditions), or into cyclopentanones (e.g., ‌150‌) with no allyl inversion in the presence of a catalytic amount of palladium(0) (‌Scheme 89‌).[‌456‌,‌457‌] The stereo- and regiochemistry of the 3-oxo esters obtained has been studied in detail.[‌458‌] As well as vinyl and allyl ethers, vinyl, and propargyl ethers can also be involved in this thermal rearrangement. In the latter case, fragile skeletons such as cephems bearing allenyl 3-oxo esters can be obtained.[‌459‌] The Claisen rearrangement is also a synthetically useful method that can be applied to an advanced bicyclic 3-oxo ester intermediate en route to bruceantin,[‌460‌] various α-allylated tetronic esters,[‌461‌] or the bicyclic 5-oxolactone ‌151‌ present in the acetoxycrenulide structure (‌Scheme 89‌).[‌462‌] Note also that the same electrocyclic transformation can be used to convert fused polycyclic enol ethers into polyfunctionalized bridged bicyclic [4.n.1]-ring systems.[‌463‌]

‌Meeeee 88‌ Meeeeee Meeeeeeeeeeeee[‌888‌,‌888‌]

Meee eee eeeeeee eee eeeeeee eeeeeeee ee eee eee-Meee eeeeeeeeeeeee eeeeeee 8-eee eeeeee. Mee eeeeeee, e eee ee 8,8-eeeeeeeeeeeeeeeeeeee, e.e. ‌888‌, ee eeeeeee ee 888°M eee 88 eeeee eeeee eee eeeeeeee eeee-eeeeeeee eeeeeee, e.e. ‌888‌ (‌Meeeee 88‌). Meeee eeeee eeeeeeeeee, eee eeeeeeeee ee eee eeee eeee, eeee 8-eee eeeee eee eeeeeee ee eeeeeeeeeeeeee eee-eeeeeeee eeeeeee ee eeeeeee eeeeeeee ee eeeeeeee.[‌888‌] Meeeeeee eee eeeeeee eeeeeee ee eeee eeeeeeee ee eeeeeeeeee eeeeeee, eeeeeeeeeeee 8-eeeeeee-8-eeeeeeeeeeeeeeeeee eeeeeeeeeee, eeeeeeeee eeee eeeeeeeee eeeeeeee. M eeeeeeeee eeeeee ee eeeeee eeeeeeee ee eeeeeeeeeeeeeee ee eeeeeeeeee ee eeeeee eeeeee ee eeeeeeee 8-(eeeeeeeeeeeeee)eeeeeeeee ee eeee-eeeeee 8-(eeeeeeeeeeeeee)eeeeeeeee eee -eeeeeeeeeee ee eeeeeeeee eeeeee.[‌888‌,‌888‌] M eeeeeeeee eeeeeeee eeeeeee eeee e eeeee eeeeeeeeeeeeee eeee eeeeeeeee ee eeeeeee eee-Meee eeeeeeeeeeeee, eeeeeee ee 8-eee eeeeee eeee e eee-Meeeeee eeeeeeee.[‌888‌] M eeeeeeee eeeeeeeee ee eee-Meee eeeeeeeeeeeee eee eeeeeeeeee (ee ee eeeeeeeeeee) ee eee eeeeeeeee eeeeeeeee eeeeeee eee ee eeee ee eee eeeeeeeee ee eee eeeeeeee eeee eeeeeeeee ‌888‌ ee eeeeeee eeeeeeeeeeeee eeeeeeee (‌Meeeee 88‌).[‌888‌]

‌Meeeee 88‌ Mee-Meee Meeeeeeeeeeeee[‌888‌,‌888‌]

Me eeeeeee ee e Meeeeee eeeeeeeeeee eeeeeeeeee eee eeeeeeee eeee eeeeeeee 8-eee eeeeee:[‌888‌] eee(MM) eeeeeeee eee eeeeeee eeeeeeeeeee eee eee eeee eeeeeeeee eee eeee eeee eeeeeee. M eee-eee eeeeeeeeeee [8,8]/[8,8]-eeeeeeeeeee eeeeeeeeeeeee eeeeeeeeee eeeeeeeeeee eeeeeeee eeee eee-eeeeee-eeeeeeee 8-eee eeeeee.[‌888‌] Mee eee eeeee eeeeeeee ee eeeeeeeeeeee eeeeeeeeeee eeeeee eeeeee eee eee eeeeeeeee eeeeeee eeeeeeeeeeee eeeeeeee. Meeeeee, e Meeeeee eeeeeeeeeeeee ee ee eeeee eeeeeee eeeeeeeee eee ee eeeeeee ee eee eeeeeeeee ee 8-eee eeeee ‌888‌ ee eeeeeeee ee eeee eeeeee (‌Meeeee 88‌).[‌888‌]

‌Meeeee 88‌ Meeeeee Meeeeeeeeeeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

Meeee 8-Meeeee-8-eeeeeeeeeeeee-8-eee-8-eeeeeeeeeee (‌888‌):[‌888‌]

M eeee ee eeeee eeeeeee ‌888‌ (8 eeee) ee 8,8-eeeeeeeeeeeeeee (88 eM) eee eeeeeeee eeeee M8 eee 88 e. Mee eeee eee eeeeee, eee eeeeeee eee eeeeeee eeeee e eeeeeee eeeeeeee (8.88 Meee), eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeee 8:88); eeeee: 88%.

References