Palladium-mediated fragmentation reactions of meta photocycloadducts to afford arylated or oxidatively cyclised products

Confirming the existence of π-allyl-palladium intermediates during the reaction of meta photocycloadducts with palladium(ii) compounds

“…Likewise the olefinic-character of cyclopropane bonds has been employed to generate p-allyl-palladium intermediates 8 from vinyl cyclopropane systems using a chloropalladation process and the mechanism of the ring-opening stage has been shown to be dependent on the reaction conditions used. 9 We have previously speculated 10,11 on the transient existence of p-allyl-palladium intermediates by the interaction of palladium(II) compounds with the vinyl cyclopropane portion of certain meta photocycloadducts and this communication provides evidence to support this mechanistic proposition.…”

“…Further investigation of the palladium-promoted chemistry of 1 revealed that it could be oxidatively cyclised to the tricycle 5 in the presence of a palladium(II) salt and again a p-allyl-palladium intermediate ( 6) was proposed to account for the transformation (Scheme 2). 11 In order to confirm the existence of a p-allyl-palladium intermediate during the reaction of a meta photoadduct with a palladium(II) salt, a model system was chosen so that it could be easily prepared and any chemical changes readily monitored using NMR spectroscopy. It was also important that the model substrate did not contain an internal nucleophile and thereby avoid intramolecular substitution reactions (see formation of 5 from 1).…”

Syntheses and Applications of Functionalized Bicyclo[3.2.1]octanes: Thirteen Years of Progress

“…Importantly, Penkett et al also described some palladium-catalyzed fragmentation reactions of anisole-derived tricyclo[3.3.0.0 2,8 ]octene meta-photocycloadducts . Under Heck arylation conditions, the anisole–allyl alcohol meta-photocycloadduct 419 was converted into the arylated products 420a , b with moderate yield and selectivity (Scheme ).…”