New Catalytic Reactions of Oxa- and Azabicyclic Alkenes

Abstract

Bicyclic alkenes, including oxa- and azabenzonorbornadienes and their derivatives, can be readily activated by transition metal complexes face-selectively due to their unsymmetrical bicyclic structure and the intrinsic angle strain on the carbon-carbon double bond. We have developed several stereo-, regio-, and chemoselective reactions catalyzed by nickel and palladium complexes using these bicyclic alkenes as substrates, providing a unique means of constructing a variety of synthetically useful carbocycles and heterocycles with high efficiency not generally accessible by traditional methods. This Account outlines these new metal-catalyzed reactions that include couplings, cycloadditions, and cyclization reactions.

Palladium-Catalyzed Homo- and Copolymerization of Polar Monomers: Synthesis of Aliphatic and Aromatic Polymers

“…Thus, we focused on a synthetic equivalent of arynes, [2.2.1]oxabicyclic alkenes, as monomers for polymerization. Although [2.2.1]oxabicyclic alkenes are useful building blocks and intermediates in organic synthesis, 89,90 they have rarely been used as monomers for polymerization. 9194 Our initial hypothesis is shown in Figure 17.…”

Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt‐Catalyzed C−H Activation and Intramolecular Nucleophilic Addition

“…Intramolecular nucleophilic addition of the C À Co bond to the amide carbonyl group followed by protodemetalation and elimination of AQ provides the final ketone product and regenerates the catalytically active Co III species.I ti sn oteworthy that the insertion of 7-oxabenzonorbornadiene (2a) into intermediate I to give II generally occurs only at the exo face of 2a,r esulting in the observed stereochemistry. [16] Furthermore,intermediate II features no suitable b-hydrogen atoms for elimination to give an olefination product, [7] and the combined steric hindrance of the AQ moiety and bicyclic alkene 2a prevents the direct reductive elimination to as ixmembered lactam. [6] In summary,wehave developed acobalt-catalyzed [3+ +2] cycloaddition of aromatic/vinylic secondary amides with bicyclica lkenes.T he reaction proceeds by coordinationassisted C À Hactivation, alkene insertion, and intramolecular nucleophilic addition.…”

Grignard Reagent Acceleration of the Intramolecular Diels–Alder Reaction of Furans with Unactivated Alkynes: Towards Structurally Complex Oxabicyclic Alkenes

“…To demonstrate the utility of oxabicycles 3 as synthetic building blocks, we investigated the ring‐opening reaction of 3 a with aryl iodides in the presence of organometallic reagents4a (Scheme ). Cheng and co‐workers have previously shown that this type of coupling reaction can be achieved by using a catalytic amount of a Pd II complex, giving rise to cis ‐dihydronaphthol derivatives 12.…”