György Göndös

Homogeneous and heterogeneous catalytic asymmetric reactions IV. Hydrogenation of the Ni complexes of cinnamic acid salts over MRNi catalyst

Abstract Substituted cinnamic acids containing a prochiral CC bond, and their Li I , K I , Ni II and Ca II salts, were prepared and their surface complexes on Ni were studied over a Raney-Ni catalyst modified with tartaric acid. The hydrogenation product of sodium cinnamate is optically active. Of the alkali metal salts of ( E )-α-phenylcinnamic acid, the hydrogenation of the Na salt gives the highest optical yield (17%). The solvent used significantly influences the selectivity. The published data for the chiral RH complexes are listed for comparison with the results of the homogeneous and heterogeneous hydrogenations described. The enantioselectivity in the presence of Raney-Ni is the result of a complex formed by the interaction of ( R,R )-tartaric acid with the substrate.

Reduction of steroid 17-ketones by enantiomeric chiral reducing agents

The reduction of steroid 17-ketones by a chiral hydrosilane–rhodium–(–)(2S,3S)-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane reagent allows greater stereoselectivity of 17α-alcohol formation than is obtained by other methods.

Stereoselective and regioselective reduction of steroid ketones by potassium tri(R,S-s-butyl) borohydride

Potassium tri(R,S-s-butyl)borohydride reduces 3-oxo-steroids of the 5α- and 5β-series to the axial alcohol under conditions in which the 17-and 20-ketone groups remain unaffected.

Transformation of compounds containing C-N bonds on heterogeneous catalysts: Part V. Hydrogenolysis of C-N bonds in substituted azacycloalkanones: preparation of sterically hindered amines and amino derivatives

Abstract On various transition metal catalysts (Raney nickel, Pd/C, Pd black, RuO2, Rh/C), the N-C(2) bond in N-benzoyl-2,2,4,4-tetraMe-azetidin-3-one (1) undergoes hydrogenolysis with 100% selectivity, as does that in the corresponding azetidine derivative 2 on Raney nickel; in the process, the oxo group in the ring in 1 is converted to a hydroxy group. In the analogues with higher numbers of ring atoms, only the latter hydrogenation proceeds; under identical reaction conditions, C-N hydrogenolysis does not occur. The rate of hydrogenolysis is increased by the carbonyl group at position 3 in azetidinone, as compared to that of azetidine, which does not possess the carbonyl function. A proposal is made concerning the reaction mechanism.

Stereochemical studies. Part 30. Synthesis and conformational analysis of deca- and dodeca-hydropyrido[2,1-b]quinazolin-11-ones

cis- and trans- Decahydro- and dodecahydro-pyrido[2,1-b]quinazolin-11-ones have been synthesized and their preferred conformations established by 1H n.m.r. spectroscopy. At room temperature the A and B rings of the cis-decahydro derivatives are conformationally mobile, while the t-butyl derivatives have fixed conformations. The predominant conformation of the cis-dodecahydro-derivatives is that in which the CO group is equatorial, the N atom is axial, and the configuration of the nitrogen bridgehead B/C fusion is trans.

Homogeneous and heterogeneous catalytic asymmetric reactions: II. Asymmetric hydrogenation of steroid ketones

Abstract The asymmetric reduction of steroid 17- and 20-ketones with chiral hydrosilanerhodium-(+)- and (−)-diop-complex catalysts allows different stereoselectivities in the formation of 17-alchols, but not of 20-alcohols. The degree of this stereoselectivity is higher than that attained with other methods. The stereoselectivity can be explained in terms of the most preferred conformation of the α-siloxysteroid-rhodium intermediate complexes.

Synthesis and stereochemistry of 8,13-diaza-2,3-dimethoxygona-1,3,5(10),9(11)-tetraen-12-one and D-homo derivatives.

From the condensation reaction of O-methylbutyrolactim (2), O-methylvalerolactim (3), O-methylcaprolactim (4) and O-methyl-4-t-butylcaprolactim (5) with ethyl 6,7-dimethoxy-alpha-[1-(1,2,3,4-tetrahydro-isoquinolyl)] acetate (1), 8,13-diaza-2,3-dimethoxygona-1,3,5(10),9(11)-tetraen-1 2-one (6) D-homo-derivatives (7-9), and medium-sized ring cyclic diamides (10,11) were obtained. The stereoselective reduction of compounds 6-9 by Adams platinum catalyst afforded 8,13-diaza-2,3-dimethoxygona-1,3,5(10)-trien-12-one (12) and its D-homo derivatives (13-15). The structures of the compounds obtained were established by NMR and X-ray crystallographic analyses.

Transformation of compounds containing C-N bonds on heterogeneous catalysis: Part IV1. Hydrogenolysis of β lactams on raney ni: a new method for the preparation of 1,3-aminoalcohols

Abstract The transformations of the condensed-skeleton β-lactams (azetidin-2-ones) 1 – 4 were studied under various reductive conditions. On the action of a complex metal hydride, selective formation of azetidines occurs. A new heterogeneous catalytic method is reported, which is suitable for the preparation of cyclic 1,3-aminoalcohols in the presence of Raney Ni in liquid-phase hydrogenation. On a Ni on Cab-O-Sil ® catalyst in a flow reactor, 1 is converted to the carboxylic acid amide 9 with high selectivity.

2-Substituted hexahydroacylanthranils: Synthesis and selective reactions with amines

SummaryIn contrast to their aromatic analogues, the corresponding saturated diamides5–9 are formed exclusively when hexahydro-3,1,4-benzoxazinones (3,4) are reacted with amines. The cyclodehydration reaction of the diamides5–9 cannot be carried out at arbitrarily high temperatures.ZusammenfassungIm Gegensatz zu den aromatischen Analoga bilden sich bei der Reaktion von Hexahydro-3,1,4-benzoxazinonen (3,4) mit Amien ausschließlich die entsprechenden gesättigten Diamide5–9. Die Cyclodehydrierungsreaktion der Diamide5–9 kann nicht bei beliebig hoher Temperatur durchgeführt werden.

Chiral hydrogenation of estrone-3-methyl ether on modified Raney nickel catalysts.

Abstract The stereochemistry of reduction of the steroid 17-ketone group by Raney nickel catalyst modified by tartaric acid depends on the chirality of the tartaric acid, the pH, and the pressure of hydrogenation.