Multicomponent reactions involving p-benzoquinones, diazo esters, titanium(IV) isopropoxide and alcohol in the presence of rhodium(II) acetate as catalyst

A Rh2(OAc)4 catalyst derived oxonium ylide intermediate underwent nucleophilic addition with the CC or CO bond of p-benzoquinones to furnish 2-substituted hydroquinones or functionalized 1-hydroxy-4-oxocyclohexa-2,5-dienyls.