Stefania Guizzetti

Highly Stereoselective Metal-Free Catalytic Reduction of Imines: An Easy Entry to Enantiomerically Pure Amines and Natural and Unnatural α-Amino Esters

A highly efficient catalytic stereoselective ketimine reduction is described. The combination of an inexpensive chiral organocatalyst, easily prepared in a single step, and of a very cheap removable chiral auxiliary allowed us to obtain enantiomerically pure amino compounds. The methodology allowed synthesis of chiral secondary and primary amines and natural and unnatural amino esters in high yields often with total control of the absolute stereochemistry.

Poly(methylhydrosiloxane)-supported chiral imidazolinones: new versatile, highly efficient and recyclable organocatalysts for stereoselective Diels–Alder cycloaddition reactions

Poly(methylhydrosiloxane) (PMHS) supported organic catalysts promoted the Diels-Alder reaction of dienes with α,β-unsaturated aldehydes, also in pure water, in yields and enantiomeric excesses comparable to those observed with the non-supported catalysts (up to 93% ee). Recycling of the catalysts was performed with no loss of enantioselectivity for at least five reaction cycles.

Enantioselective catalytic reduction of ketoimines with trichlorosilane promoted by readily available chiral Lewis bases

The straightforward synthesis of a series of enantiomerically pure Lewis basic amides by simple condensation of commercially available enantiopure diamines with picolinic acid is reported. These compounds were shown to promote the enantioselective reduction of ketoimines with trichlorosilane. Working with the model substrate N-phenyl benzophenone imine, the new organocatalysts led to the formation of the corresponding amine, with excellent chemical efficiency (up to 99% chemical yield) and good stereoselectivity (up to 73% ee). Up to 83% of enantioselectivity was reached in the reduction of differently substituted imines.

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

Abstract 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 α,β-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 α-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.