Direct generation of lithium homoenolates from 3-aryl alpha,beta-unsaturated ketones or esters by an arene-catalysed lithiation: Synthesis of substituted tetrahydrofurans and gamma-butyrolactones

The reaction of alpha,beta-unsaturated ketones 1 with an excess of lithium powder, a catalytic amount of naphthalene (4 %) and different carbonyl compounds in the presence of boron trifluoride in THF at -78 - 0 degrees C yields, after treatment with silyl nucleophile and final hydrolysis, the expected substituted tetrahydrofurans 5. Similar methodology applied to beta-aryl acrylic esters 6, but without using boron trifluoride or silyl reagents yields the corresponding lactones 7. (C) 1997, Elsevier Science Ltd.