Synthesis and some transformations of 4-aryl-substituted amines of the tetrahydropyran series

The reaction of 2-isopropyltetrahydropyran-4-one [obtained by isomerization and hydration of 3-isopropylpent-1-en-4-yn-3-ol in the presence of 5% sulfuric acid and mercury(II) sulfate] with ethyl cyanoacetate gave ethyl cyano(2-isopropyltetrahydropyran-4-ylidene)acetate which was treated with 4-tolylmagnesium chloride. The resulting ethyl cyano[2-isopropyl-4-(4-tolyl)tetrahydropyran-4-yl]acetate was subjected to decarbethoxylation to obtain 2-isopropyl-4-(4-tolyl)tetrahydropyran-4-ylacetonitrile. The latter was reduced to the corresponding amine with lithium tetrahydridoaluminate, and the reduction product was brought into condensation with aromatic aldehydes. The Schiff bases thus formed were reduced with sodium tetrahydridoborate, followed by N-acylation with acetyl and propionyl chlorides.