Massimo Falorni

Mild Reduction of Carboxylic Acids to Alcohols Using Cyanuric Chloride and Sodium Borohydride

Several carboxylic acids, including N-Boo, N-Cbz and N-Fmoe amino acids were reduced to the corresponding alcohols by activation of the carboxy function with cyanuric chloride and N-methylmorpholine followed by reduction with aqueous sodium borohydride.

Chiral ligands containing heteroatoms. 8. 2-[(2s)-2-pyrrolidinyl]pyridine as a novel catalyst in the enantioselective addition of diethylzinc to aldehydes

Abstract The title compound has been demonstrated to be an effective enantioselective catalyst in the addition of diethyizinc to aldehydes: optically active secondary alcohols in up to 100% ee were obtained in high yields. The temperature dependence of the stercodynamic course of the reaction was examined and the nature of the possible catalytic complex was discussed on the basis of NMR data too.

Chiral ligands containing heteroatoms. 10. 1-(2-pyridyl)alkylamines as chiral catalysts in the addition of diethylzinc to aldehydes: temperature dependence on the enantioselectivity.☆

Abstract Chiral amino pyridines derived from α-aminoacids were demonstrated to be enantioselective catalysts in the addition of diethylzinc to aldehydes: optically active secondary alcohols in up to 98% ee were obtained in high yields. The temperature dependence of the stereochemical course of the reaction was found to be strictly related to the alkyl structure of the chiral catalyst. The nature of the possible catalytic complex and the origin of temperature effect was thus discussed on the basis of NMR data too.

Chiral ligands containing heteroatoms. 14. 1,3-oxazolidinyl methanols as chiral catalysts in the enantioselective addition of diethylzinc to aldehydes

Abstract Starting from l -serine and l -threonine, (S)-diphenyl-(2,2-dimethyl-1,3-oxazolidin-4-yl)-methanol and (4S,5R)-diphenyl-(2,2-dimethyl-5-methyl-1,3-oxazolidin-4-yl)-methanol were prepared in good yields. The use of these compounds as very efficient chiral catalysts for the enantioselective addition of diethylzinc to aldehydes is described. This paper reports the first example of the use of oxazolidine methanols in asymmetric synthesis.

Chiral ligands containing heteroatoms. 6. 1-(2-Pyridylmethyl)pyrrolidine in the chiral catalysis of addition of diethylzinc to benzaldehyde.

Abstract The synthesis of a series of new optically active pyridine ligands from proline derivatives has been developed for the enantioselective addition of dialkyl zinc compounds to aldehydes. The results obtained indicate that the coordination of a metal atom to the nitrogen of the pyridine ring is essential in determining the stereochemistry of the process.

Chiral ligands containing heteroatoms. 11. Optically active 2-hydroxymethyl piperazincs as catalysts in the enantioselective addition of diethylzinc to benzaldehyde

Abstract Starting from enantiomerically pure serine, a series of (2 R ,5 S ) and (2 S ,5 S )-2-hydroxymethyl-5-alkyl piperazines 1–5 were prepared in good yields without any racemization. The use of these compounds as chiral catalysts for the enantioselective addition of diethylzinc to aldehydes is described. This paper reports the first example of the use of piperazine methanols in asymmetric synthesis.

Synthesis of chiral pyrazoles and isoxazoles as constrained amino acids

Abstract A stereospecific syntheses of optically active pyrazoles and isoxazoles from L-proline is described. The procedure presented is based on readily available materials and can be used for preparing new conformationally restricted pyrazole-containing amino acids.

Optically active 4-oxaroline derivatives: New useful chiral synthons derived from serine and threonine

Abstract A very simple procedure for the preparation of chiral optically active N-protected-4-carboxy-1,3-oxazolidine (4-oxaproline) derivatives starting from serine and threonine is described which avoids the use of toxic solvents or reagents. Elaboration of these compounds allows significant improvement in the handling of serine and threonine during the multigram preparation of oligopeptide structures and affords versatile chiral building blocks for the organic synthesis.

Chiral ligands containing heteroatoms. III. Enantioselective ketone reductions using tin(II) organometallic systems from chiral piperazines

Abstract Chiral reducing agents were prepared from stannous chloride, optically active piperazines as ligands and diisobutylaluminium hydride; these complexes were effectively employed in the asymmetric reduction of prochiral ketones.

Synthesis of C2-symmetry 2,2′-bipyridine and 1,10-phenanthroline chiral ligands bearig the 6,6-dimethylnorpinan-2-aryl group

Abstract 6-(1S,2S)-6,6-dimethylbicyclo(3.1.1]hept-2-yl)-2-6-(1S,2S)-6, 6-dimethylbicyclo (3.1.1)hept-2-yl-pyridin-2-yl-pyridine (5), 2,9-bis (1S,2S)-6,6-dimethylbicyclo (3.1.1)hept-2-yl-5,6-dihydro-1, 10-phenanthroline (11) and 2,9-bis(1S,2S)-6, 6-dimethylbicyclo(3.1.1]hept-2-yl)-1,10-phenanthroline (12), three new chiral nitrogen ligands of C2 symmetry have been prepared.