15351-09-4

The iridium-f-amphox-catalyzed asymmetric hydrogenation of racemic α-amino β-unfunctionalized ketones proceeds via a DKR (dynamic kinetic resolution) process for the construction of various chiral N,N-disubstituted α-amino β-unfunctionalized alcohols in quantitative yields with excellent enantioselectivities and diastereoselectivities (all products >99% ee and >99:1 dr, TON up to 100 000). Importantly, this catalytic asymmetric hydrogenation with a DKR process provided a highly efficient and powerful synthetic strategy for the preparation of key chiral intermediates of the preclinical antitumor agent (S,S)-R116010.

An N-Bromosuccinimide (NBS) promoted one pot strategy for the synthesis of α-amino functionalized aryl ketones starting from commercially available styrenes has been developed. NBS participates in multiple tasks, such as bromonium ion formation, oxidation of bromohydrin and providing a nucleophilic nitrogen source. The reaction can easily be switched between α-imido and α-amino ketones by the choice of base. This one pot strategy was successfully applied for the synthesis of psychoactive drug candidates, amfepramone, mephedrone and 4-MEC.

The racemic tertiary cathinones N,N-dimethylcathinone (1), N,N-diethylcathinone (2) and 2-(1-pyrrolidinyl)-propiophenone (3) have been prepared in reasonable yield and characterized using NMR and mass spectroscopy. HPLC indicates that these compounds are isolated as the anticipated racemic mixture. These can then be co-crystallized with (+)-O,O′-di-p-toluoyl-d-tartaric, (+)-O,O′-dibenzoyl-d-tartaric and (-)-O,O′-dibenzoyl-l-tartaric acids giving the single enantiomers S and R respectively of 1, 2 and 3, in the presence of sodium hydroxide through a dynamic kinetic resolution. X-ray structural determination confirmed the enantioselectivity. The free amines could be obtained following basification and extraction. In methanol these are reasonably stable for the period of several hours, and their identity was confirmed by HPLC and CD spectroscopy.

Ynolates were found to react with α-alkoxy-, α-siloxy-, and α -aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the β-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z selectivity is in duced by orbital and steric interactions rather than by chelation. In a similar manner, α-dialkylamino ketones provided olefins with excellent Z selectivity. These products can be easily converted into multisubstituted butenolides and γ-butyrolactams in good yield.

The ultracentennial 10-I-4 iodinane oxide IBX (3; o-iodoxybenzoic acid; 1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide) represents a new oxidizing reagent that successfully joins to the large family of known oxidants.IBX, in contrast to other valuable oxidants, is inexpensive to prepare and easy to handle, can tolerate moisture and water, and generally gives very good yields.Furthermore, IBX is mild and chemoselective (primary alcohols are converted into aldehydes with no overoxidation to acids; 1,2-diols are converted to α-ketols or α-diketones without oxidative cleavage; amino alcohols are oxidized to amino carbonyls, without protection of the amino group; sensitive heterocycles are not affected; various other functional groups are compatible with IBX oxidation).IBX is versatile (it works in various solvents and it is highly sensitive to temperature variations), and its solutions in DMSO are stable enough to carry out the oxidation reaction easily.

The equilibrium constants and rate constants for the dissociation of the 2,3-bis(dialkylamino)-1,4-diketone diastereomers meso- and DL-7a and 7b were measured over a temperature range of 40 deg C.From the enthalpies of dissociation ΔHDiss and ethalpies of activation ΔH(excit.) and the strain enthalpies of 7 the bond dissociation enthalpies BDE(C-C) of 7 were determined.By comparison with the dissociation enthalpies of Ct-Ct alkanes the change of these BDEs(C-C) by the capto-dative substitution was determined to be 85.4 kJ mol-1 (20.4 kcal mol-1).The heats of formation ΔHf0(g) of a series of amino ketones 8 were determined from their heats of combustion and their heats of evaporation.From the ΔHf0(g) values in combination with MM2 calculations of their strain enthalpies strain-free increments CHn2-n> with n = 0, 1, 2 were derived and geminal interaction enthalpies in the ground states were obtained thereof.The radical stabilization enthalpy RSE of 6 was deduced from the ΔBDE(C-C) values and the ground state effect to be 73.6 kJ mol-1 (17.6 kcal mol-1).From these data and the radical stabilization enthalpies RSE of α-aminoalkyl radicals (4.2 kJ mol-1) and α-carbonyl radicals (28.9 kJ mol-1) a synergetic radical stabilization enthalpy of 40.5 kJ mol-1 (9.7 kcal mol-1) is deduced.This number combines "extra" resonance stabilization and general inductive or anomeric geminal substituent interaction in the radicals.The crystal structure of meso-7a has been determined by X-ray diffraction methods. - Key Words: C-C Bond cleavage, kinetics of / Heats of formation / Radicals, stability of / Capto-dative effect / Geminal substituents, energetic interaction of

The reduction of aminoketones and aziridinoketones with zinc borohydride is highly stereoselective.The zinc atom is complexed only by nitrogen atoms of reduced molecules.There is no chelate formation with the participation of carbonyl groups.