A potentially general regiospecific synthesis of substituted quinones from dimethyl squarate

TLDR: In this article, a potentially general regiospecific synthesis of benzo- and naphthoquinones is described, which starts with dimethyl squarate (1), which is converted to the cyclobutenone ketal 9 upon sequential treatment with an organolithium reagent and then BF 3 etherate or TFAA in THF/methanol.

Abstract: 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 9 upon sequential treatment with an organolithium reagent and then BF 3 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-hydroxycyclobutenones 7-9 and these readly 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