Ethyl 3-benzoylamino-2-oxo-6-triphenylphosphoranylidenemethyl-2H-pyran-5-carboxylate (1) reacts with 2-nitrobenzaldehydes (2) to give 6-(2-nitrostyryl)-2H-pyran-2-ones (3), as the E stereoisomers, in good yields. The reduction of compounds 3, performed with hydrogen over Pd/C at room temperature and 1 atmosphere, leads to a mixture of 2-amino-4-tetrahydroquinolinylidene-2-pentenedioic acid derivatives 5a-d as the main products, the corresponding 3-butenoic acid derivatives 6 and a minor amount of pyrano[2,3-c]benzazocines 9a-c. At 40 atmospheres and 900, the reduction gives 4-amino-2-tetrahydroquinolinylbutanoic acid derivatives 8a-d as the main products and their precursors 7a,b,d as the minor ones. Amines 4c,d are isolated by stopping the reduction after the uptake of 3 equivalents of hydrogen.
