SEARCH Articles Figures Tables Diels acid Diels hetero Diels-Alder reaction acids Hetero Diels-Alder reaction chiral Lewis acids Hetero Diels-Alder reaction intramolecular Lewis acid Hetero Diels-Alder reaction intramolecular Lewis acid catalysed Hetero-Diels-Alder Hetero-Diels-Alder reaction Lewis acids Diels-Alder reaction Lewis reactions