Isophthalic Acid-Derived Dicarbothioamides as Novel Metal-Free Catalysts in Hydrogen Bond-Promoted Reactions

The synthesis of N,N'-diaryl-1,3-benzene-dicarbothioamides was accomplished in only two steps with good yields, and their ability to act as hydrogen-bond donors in Diels-Alder reactions was evaluated. These new organocatalysts were indeed able to promote the cycloaddition of cyclopentadiene to ,-unsaturated aldehydes. In the attempt to control the absolute stereochemistry of the reaction, chiral catalysts were also prepared by simple condensation of isophthalic acid and -amino acid derivatives. Molecular mechanics calculations were performed to elucidate the mode of action of these metal-free catalytic systems and to find a rationale for the achieved enantioselectivity