Allylic Functionalization of 2,5- and 2,4-Cyclo-Hexadiene-1,3-Dicarboxylates

Abstract

A series of 2,4- and 2,5-cyclohexadiene-1,3-dicarboxylates were functionalized at the allylic position via oxidation (SeO₂, PDC/t-BuOOH) and halogenation (NBS). The regiochemical outcome for different substrates and reactions was studied and the importance of factors such as reaction mechanism, steric hindrance and reaction intermediates stability was discussed.

^§Present address: GlaxoWellcomc Medicines Research Centre, Via Fleming 4, Verona, Italy

^$Present Address: Hoechst Marion Roussel, Paris, France

Notes

^§Present address: GlaxoWellcomc Medicines Research Centre, Via Fleming 4, Verona, Italy

^$Present Address: Hoechst Marion Roussel, Paris, France

The same reaction was performed also in Ref. 10, but formation of peroxides 20a,b was not reported

All the aspects related to stereoselectivity (see relative abundancies of the various diastereomeric couples) were not clarified in this work. The more abundant diastereomeric couple was called a (for example, 14a) and the less abundant was named b, as 14b. The attribution of a and b stereoisomers in the couples derived from compounds 4—10 was done accordingly to what was seen for alcohols 14—16 and bromides 17—19 (¹H NMR)