Background Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate capable of undergoing multiple types of transformations due to three key structural features: a free alkene, a bridged oxygen atom, and a highly strained ring system. Most notably, ring-opening reactions of OBD using transition metal catalysts and nucleophiles produce multiple stereocenters in a single step. The resulting dihydronaphthalene framework is found in many natural products, which have been shown to be biologically active. Objective This review will provide an overview of transition metal-catalyzed reactions from the past couple of years including cobalt, copper, iridium, nickel, palladium and rhodium- catalyzed reactions. In addition, the recent derivatization of OBD to cyclopropanated oxabenzonorbornadiene and its reactivity will be discussed. Conclusion It can be seen from the review, that the work done on this topic has employed the use of many different transition metal catalysts, with many different nucleophiles, to perform various transformations on the OBD molecule. Additionally, depending on the catalyst and ligand used, the stereo and regioselectivity of the product can be controlled, with proposed mechanisms to support the understanding of such reactions. The use of palladium has also generated a cyclopropanated OBD, with reactivity similar to that of OBD. An additional reactive site exists at the distal cyclopropane carbon, giving rise to three types of ring-opened products.

Recent Advances in Transition Metal-Catalyzed Reactions of Oxabenzonorbornadiene.

The palladium/Lewis acid cocatalyzed ring-opening reaction of various C1-substituted unsymmetrical oxabenzonorbornadienes (OBD) with oxime nucleophiles was investigated. The effects of various C1 substituents were explored. Moderate to excellent yields and excellent regioselectivities were obtained for electron-withdrawing groups. The presence of electron-donating alkyl groups leads to isomerization of the corresponding OBD to afford the substituted naphthol derivatives. Additionally, a mechanism for the formation of C2 regioisomeric ring-opened products has been proposed.

Palladium/Lewis Acid Cocatalyzed Ring-Opening Reactions of Unsymmetrical Oxabenzonobornadienes with Oximes.

Intramolecular Palladium-Catalyzed Ring Opening of Oxabenzonorbornadienes with C1-Tethered Aryl Halides.

Iridium-catalyzed ring-opening reactions of unsymmetrical oxabenzonorbornadienes with water and alcohol nucleophiles

A DFT Study on the Mechanism and Origin of Regioselectivity in the Rhodium/Diene-Catalyzed Ring-Opening Reactions of C1-Substituted Oxabenzonorbornadienes with Arylboronic Acids

The effect of ethyl and methoxycarbonyl substitution on the C1 position of oxabenzonorbornadienes undergoing palladium-catalyzed nucleophilic ring opening was investigated with a variety of aryl io...

EdmundsMichael

Papers

Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabenzonorbornadienes