A Potentially General Regiospecific Synthesis of Substituted Quinones from Dimethyl Squarate

Article abstract of DOI:10.1021/jo00051a040

A potentially general regiospecific synthesis of benzo- and naphthoquinones is described.This method starts with dimethyl squarate (1) which is converted to the cyclobutenone ketal 3 upon sequential treatment with an organolithium reagent and then BF3 etherate or TFAA in THF/methanol.Treatment of these with a second lithium reagent followed by hydrolysis gives the cyclobutenones 5.Addition of an alkynyl-, alkenyl- or aryllithium agent to 5 followed by hydrolysis of the ketal linkage gives the corresponding 4-alkynyl-, 4-alkenyl- or 4-aryl-4-hydroxycyclobutenones7 - 9, and these readily rearrange to the respective quinones or hydroquinones upon thermolysis in refluxing benzene.In a similar fashion, 15 was employed as a reagent to prepare mono- and disubstituted hydroquinones and quinones.