Gerardo Aguirre

SYNTHESIS OF CHIRAL SULFONAMIDE/SCHIFF BASE LIGANDS

Abstract We report a facile two step synthesis of chiral ligands for bonding to transition metals. The ligands are easily prepared from trans -1,2-diaminocyclohexane by reaction with sulfonyl chlorides to give amino-sulfonamide compounds. These intermediates are then condensed with salicylaldehyde derivatives to provide sulfonamide/Schiff base compounds which represent a new class of chiral ligands.

Synthesis, characterization, and structure of dinuclear copper(I) and silver(I) complexes of ortho-functionalized 1,3-bis(aryl)triazenide ligands

Abstract The synthesis, characterization, and crystal structures of dinuclear copper(I) and silver(I) complexes with a functionalized 1,3-diaryl triazenide ligand are reported. The triazene ligand is substituted with carboxymethyl groups in the ortho positions of the aryl rings that can coordinate to electron deficient metals. Reaction of this ligand with Cu(OAc) and Ag(OAc) resulted in the formation of dinuclear complexes with an eight-membered ring core composed of the two triazenide ligands and two metals. In these complexes, only one carbonyl group of each triazenide ligand binds to the metal centers.

Steric effects in the design of chiral Schiff base–titanium complexes: new catalysts for asymmetric trimethylsilylcyanation of aldehydes

New chiral Schiff base ligands derived from salicylaldehydes bearing bulky ring substituents were synthesized by reaction with various amino alcohols. These new ligands were used with titanium tetraisopropoxide to study steric effects on the enantioselectivity of the trimethylsilylcyanation of aldehydes.

Synthesis of racemic cis and trans 2,4,5-tripyridylimidazolines

Abstract Reaction of 2-pyridinecarboxaldehyde with ammonium hydroxide gives 1,3,5-triazine 6 which was converted to cis-2,4,5-tripyridylimidazoline, 9 . The intermediate 2,4-diazapentadiene is not observed, but believed to undergo deprotonation and cyclization to afford cis-2,4,5-tripyridylimidazoline. Base catalyzed isomerization (5 mol% KO-t-Bu, 23°C) of cis-2,4,5-tripyridylimidazoline gives trans-imidazoline ( 10 ). Compounds 6 , 9 , and 10 have been characterized by X-ray crystallography.

SYNTHESIS AND STRUCTURE OF A DINUCLEAR COPPER COMPLEX OF A BIS(BIDENTATE)TRIAZENIDE LIGAND

Abstract The synthesis and characterization of a dinuclear copper(II) complex with a bis(bidentate) ligand is reported. The ligand is a functionalized 1,3-diaryl triazene substituted with carboxymethyl groups at the ortho positions of the aryl rings. Reaction of this ligand with Cu2(OAc)4·2H2O resulted in the formation of the Cu2(OAc)3(triazenide) where the triazenide binds to each copper through one of the triazenide nitrogens and the carbonyl oxygen of the pendant esters. The structures of this dinuclear complex and of the ligand are reported.

Asymmetric synthesis of amathamides A and B: novel alkaloids isolated from Amathia wilsoni

Abstract Syntheses of the amathamides A and B ((2S)-N-[(E and Z)-2(2,4-dibromo-5-methoxyphenylethenyl]-1-methyl-2-pyrrolinecarboxamides), new alkaloids isolated from the Tasmanian marine bryozoan Amathia wilsoni, were accomplished by a sequence of reactions starting from 3-hydroxybenzaldehyde.

Synthesis of chiral heteroaromatic tetradentate sulfonamide based ligands

Abstract We report a facile two step synthesis of chiral tetradentate ligands for late metal complexes. The ligands are easily prepared from trans-1,2-diaminocyclohexane or chiral 1,2-diphenylethylenediamine and a heteroaromatic sulfonyl chloride in the presence of base (K2CO3 or Et3N). These compounds represent a new class of chiral tetradentate N2S2 and N4 based ligands.

Synthesis of Deuterium-Labeled Antihypertensive 3-(4-Phenyl-1′-Piperazinyl)-Propyl-2,4-Quinazolinedione

Abstract Synthesis of deuterium-labeled 3-(4-phenyl-1-piperazinyl)-propyl-2,4-quinazolinedione (Pelanserine) an anti-hypertensive agent.

Asymmetric Transfer Hydrogenation of Prochiral Ketones in Aqueous Media with Chiral Water-Soluble and Heterogenized Bifunctional Catalysts of the RhCp*-Type Ligand

Asymmetric transfer hydrogenation (ATH) of prochiral aromatic ketones was carried out with a water-soluble complex of Rh(III)Cp* and mononitrobenzenesulfonamide bidentate ligand (1R,2R)-N-(2-aminocyclohexyl)-4-nitrobenzenesulfonamide 1 derived from chiral cyclohexane-1,2-diamine. Aqueous sodium formate was used as the hydride source. The reaction afforded the chiral alcohols in good enantioselectivities (79-93%) and yields (>99%). The modified monosulfonamide ligand was also covalently immobilized on solid phase such as silica, resin, and mesoporous SBA-15 silica and then explored as a catalyst with Rh(III)Cp* in the ATH of acetophenone.

Montmorillonite-K10 Catalyzed Addition OF Trimethylsilylcyanide (TMSCN) to Aldehydes.

Abstract Addition of trimethylsilyl cyanide (TMSCN) to aldehydes was catalyzed by Montmorillonite-K10, with subsequent reduction to β-aminoalcohol.