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

摘要

Whilst seeking to improve the yield of a Heck-style arylation/fragmentation reaction using a silyloxy substituted meta photocycloadduct, an alternative reaction pathway was discovered that led to the formation of the unique oxidatively cyclised compound 8. This tricyclic ether is believed to form as the result of the meta photocycloadduct structure fragmenting to give a pi-allyl palladium species and then subsequently being displaced by a neighbouring hydroxyl group. An attempt to develop an enantioselective version of this reaction via the desymmetrisation of a meso pi-allyl palladium intermediate was made using the meta photocycloadduct derived from anisole and Z-but-2-ene-1,4-diol, however no enantioenrichment of the products could be detected. (c) 2006 Elsevier Ltd. All rights reserved.