Merging Manganese and Iminium Catalysis: Selective Hydroalkenylation of Unsaturated Aldehydes and Ketones

The use of synergistic catalytic strategy can usually circumvent the intrinsic limitations of one catalytic system. In this communication, we disclose a cooperative catalysis strategy of manganese and iminium catalysis to realize selective hydroalkenylation of unsaturated aldehydes and ketones. Its success stems from the LUMO activation of unsaturated carbonyl compounds with secondary amines as the organocatalyst and the synergistic HOMO activation of alkenylboronic acids with Mn2(CO)8Br2. This protocol exhibits several synthetic advances, e.g., simple operation, good functional group compatibility and good regioselectivity. The theoretical calculation indicates the migratory insertion followed by demetallation-isomerization process is kinetically more favorable than Michael-like nucleophilic addition. The use of proline-derived organocatalyst can deliver the desired products in moderate enantioselectivity. Selective hydroalkenylation of unsaturated aldehydes and ketones has been accomplished via synergistic HOMO and LUMO activation by means of manganese and iminium catalysis. The use of chiral organocatalysts could provide the corresponding products with moderate enantioselectivity.+image

Automated summary

This study achieved the selective hydroalkenylation of unsaturated aldehydes and ketones using a cooperative catalysis strategy involving manganese and iminium catalysis. The method exhibits several advantages such as simple operation, good functional group compatibility, and good regioselectivity.