SEARCH Articles Figures Tables Diels acid Diels-Alder catalysis Diels-Alder reaction acids Diels-Alder reaction catalysis by Lewis acids Diels-Alder reactions catalysis Diels-Alder reactions non-Lewis acid catalysis Intermolecular Diels-Alder reactions Lewis acid catalysis Lewis acids Diels-Alder reaction Lewis acids acid catalysis Lewis acids catalysis of Diels-Alder reactions Lewis acids, catalysis Lewis acids, catalysis in Diels—Alder reaction Lewis catalysis Lewis reactions