Nickel‐Catalyzed Asymmetric [2+2] Cycloaddition Reaction of Hetero‐Bicyclic Alkenes with Internal Alkynes

Abstract

Enantioselective [2+2] cycloaddition reaction of azabenzonorbornadienes and oxabenzonorbornadienes with internal alkynes has been enabled by a catalyst system comprising Ni(COD) and (R)-SIPHOS-Ph-Mor. This transformation represents the first asymmetric [2+2] cycloaddition reaction of azabenzonorbornadienes with internal alkynes, providing a straightforward method to prepare four-membered carbocycles.

Gold-Catalyzed Synthesis of Small Rings

“… 690 , 692 , 695 This becomes particularly challenging when alkynes 719 are used in place of allenes. 720 , 721 This approach has been developed using Co, 722 Zn, 723 Ni, 724 Cu, 725 − 729 Ru, 730 − 733 Rh, 734 Pd, 735 and Ir 736 , 737 catalysts using either cyclic alkenes or alkenes substituted with electron-withdrawing groups. In this context, Echavarren and co-workers reported the enanatioselective gold(I)-catalyzed synthesis of cyclobutenes by [2 + 2] cycloaddition between alkynes and alkenes using non- C 2 symmetric Josiphos chiral ligands ( Scheme 154 ).…”

Lewis Base‐Catalyzed Cycloaddition of Heterocyclic Alkenes with 2,2,2‐Trifluorodiazoethane (CF3CHN2): Access to Trifluoromethylated Pyrazolines and Pyrazoles

“…Due to the angle strain and the proximal heteroatom coordination, heterobicyclic alkenes are versatile synthetic building‐blocks for the construction of complex cyclic frame works in various types of organic transformations including metal‐catalyzed cycloaddition reactions, [10a–g] metal‐catalyzed C−H addition and annulations, [10h–j] ring opening reactions [10k–l] . Oxa ‐ and aza‐ bicyclic alkenes, such as oxa ‐ and aza ‐benzonorbornadienes, have been recognized as useful building blocks in molecular architecture as they can serve as general templates to create highly substituted ring systems [11] .…”

Versatile Catalytic Reactions of Norbornadiene Derivatives with Alkynes

“…Recently, our group reported the first asymmetric [2+2] cycloaddition reaction of azabenzonorbornadienes and oxabenzonorbornadiene with internal alkynes. The reaction provides a straightforward method for the synthesis of four‐membered carbocycles with multiple chiral centers . The reaction proceeded under the catalytic system of Ni(cod) 2 and ( R )‐SIPHOS‐Ph‐Mor and the cycloaddition products were obtained in moderate to high yields with up to 92% enantioselectivity [Eq.…”