4,5-Dibenzyloxybenzyne as a synthon for diels-alder reactions. The synthesis of 6,7-dihydroxy-1,4-ethano-1,2,3,4-tetrahydroisoquinolines as rigid analogs of adrenergic agents. Assignment of proton and carbon-13 NMR parameters using homonuclear and heteronuclear two-dimensional chemical shift correlation NMR spectroscopy

The synthesis of several rigid analogs of catecholamine type of adrenergic agents is reported. Their synthesis began with a Diels-Alder cycloaddition of 4,5-dibenzyloxybenzyne (generated from 4,5-dibenzyloxyan-thranilic acid) to 1-(2-trans-phenylvinyl)-2-pyridone and 1-benzyl-3-benzyloxy-2-pyridone. The unsaturated amides so produced were reduced first with hydrogen and palladium and then with lithium aluminum hydride to provide 6,7-dihydroxy-1,4-ethano-1,2,3,4-tetrahydroisoquinolines. Homonuclear and heteronuclear two-dimensional chemical shift correlation nmr spectroscopy confirmed the structure of the bridged tetra-hydroisoquinolines and led to the unambiguous assignment of the ¹H and ¹³C nmr chemical shifts of key compounds.