Asymmetric Regiodivergent Allylic Alkylation Reactions Of The MBH Adducts

Asymmetric allylic alkylation (AAA) is one of the most useful reactions in organic synthesis which allows easy access to chiral allylic intermediates. Especially via organocatalytic methods utilizing Morita-Baylis-Hillman (MBH) adducts as an electrophilic allylation reaction partner have recently emerged as a powerful strategy. The majority of reactions in this category made use of a cascade Sn2’-Sn2’ pathway initiated by a nucleophilic phosphine or amine catalyst. On the other hand, the nucleophile can also via an addition-elimination pathway or Sn2’-Sn2 pathway, leading to the formation of allylation products with different regioselectivity. While the literature examples of this pathway for the construction of allylation products are scarce. Therefore using the versatile catalytic AAA reactions yielding different regioisomers are certainly very appealing and are of enormous synthetic value. For the first time, we set out to explore the application of pyrazolone derivatives as a novel reaction partner with the MBH adducts in the AAA reaction. Highly enantioselective regiodivergent synthesis allylic alkylation products were achieved by an Sn2’-Sn2 process, employing tertiary amine as the catalyst.