1,2-Di(lithiomethyl)benzene from Phthalan: Sequential Introduction of Two Different Electrophiles

Article abstract of DOI:10.1016/0040-4020(95)00064-F

The reaction of phthalan (1) with an excess of lithium powder and a catalytic amount of DTBB (2.5 mol percent) in THF at 20 deg C followed by treatment with electrophiles (D2O, CO2 and carbonyl compounds) at -78 deg C leads, after hydrolysis, to the corresponding functionalised benzylic alcohols 3a-g.When the lithiation reaction is continued, after the reaction with the first electrophile, and a second electrophile (H2O, D2O and carbonyl compounds) is added, the corresponding disubstituted compounds 6a-q are prepared.Diols 3c-g and 6h,i,l,n and hydroxyacids 6a,c,f,k are easily dehydrated to the corresponding cyclic ethers (7c-f, 8h,i,l,n) or lactones (9a,c,f,k) respectively.Finally, alcohols 6b,d,e give, after acid treatment, the Friedel-Crafts type benzocyclopentenes 10b,d,e.