Christian Rømming

Studies on organophosphorus compounds—XL: Reactions of ketones with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide☆

Abstract Cyclohexanone and cyclopentanone react with 2,4 - bis - 4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane 2,4-disulfide (lawesson Reagent ( LR ) at 80° with formation of new spiro - 1,3,5,2 - trithiaphosphorines 1 and 2 , respectively. 2-Methyl and 2-phenylcyclohexanone also react with LR at 80° producing the enethiols 3 and 4 , which on storage are transformed into the sulfides 5 and 6 . Unsaturated cyclohexanones 7–9 are transformed into the corresponding thioketones 10–12 after reactions with LR at 60° for a few hours. 2-Hydroxyketones react with LR with formation of 1,3,2-oxathiaphospholes and similarly a 2-aminoketone gave a 1,3,2-thiazaphosphole. Aromatic ketones, reacted with LR to give corresponding thioketones. Thiofluorenone dimerized to form the cyclic disulfide 31 , as proved by X-ray analyses.

RU(II)-CATALYZED RING CLOSING METATHESIS IN STEREOSELECTIVE SYNTHESES OF CONSTRAINED HOMOSERINE ANALOGUES

Abstract Stereoselective syntheses of cyclic α-amino-°-hydroxycyclohexene- and cycloheptene-α-carboxylic acids are described. RCM cyclization reactions were effected by Ru(II)-catalysis on sterically homogenous hydroxylated dienes. The diene substrates were available by stepwise, stereoselective alkylations of (R)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine with bromoalkenes, ethylene oxide and subsequent transformations.

Isolation and characterization of 3-methoxy-2(5H)-furanone as the principal nephrotoxin from Narthecium ossifragum (L.) Huds.

The principal substance in Narthecium ossifragum (L.) Huds, responsible for the nephrotoxic effects on cattle, moose, goats and other ruminants has been isolated and identified by X-ray crystallography as 3-methoxy-2(5H)-furanone. The Fourier-transform infra-red, 1H and 13C nuclear magnetic resonance, and mass spectra are also given. The concentration in four different batches of plant material varied from 113 to 344 microg g(-1) (wet weight). Extracts of N. ossifragum and fractions derived from them, including purified 3-methoxy-2(5H)-furanone, were each dosed intraruminally, to young goats. 3-Methoxy-2(5H)-furanone of 99.9% purity (15 mg kg(-1) live weight) caused increased concentration of creatinine in serum within 2-3 days, typical of kidney damage caused by N. ossifragum, while toxic effect was obtained down to 4 mg kg(-1) live weight with less purified material (> or = 95%). Toxic effect was also obtained with synthesized 3-methoxy-2(5H)-furanone (30 mg kg(-1) live weight). The isomer 4-methoxy-2(5H)-furanone, detected in some of the batches of the plant material, was not toxic when dosed at 60 mg kg(-1) live weight.

The crystal structure of AuNi2Sn4

A hitherto unknown, virtually stoichiometric phase with composition AuNi2Sn4 has been identified in the AuNiSn system, and its structure has been determined by direct methods. The unit cell is rhombohedral (space group: R3m) with dimensions a = 422.6(1) pm and c = 2656.6(4) pm in the hexagonal setting and a = 918.2(2) pm and α = 26.60(1)° in the rhombohedral setting. According to the hexagonal description Au is in 3b and Ni, Sn(I), and Sn(II) are in 6c with z = 0.40091(6), 029965(3), and 0.11204(3), respectively. AuNi2Sn4 proves to be isostructural with the mineral smythite (Fe3S4-s). The Fe3S4-s-type structure belongs to the NiAs-type family and certain aspects of the structural relationships are briefly discussed.

Reversible heterolytic CH cleavage by intramolecular CH activation at diazabutadiene ligands at iridium

Abstract Reactions between [Cp∗IrCl2]2 and diaryl-substituted diazabutadienes (dab) ArNCR′CR′NAr (R′=H: Ar=4-MeC6H4, 2,6-Me2C6H3, 2,6- i Pr 2 C 6 H 3 ; R′=Me: Ar=4-MeC6H4) proceed straightforwardly to give the dab complexes Cp∗Ir(dab)Cl+Cl−. Sterically more encumbered dab ligands (R′=Me: Ar=2,6-Me2C6H3, 2,6- i Pr 2 C 6 H 3 , 2,4,6-Me2C6H3) instead give products Cp ∗ IrClCH 2 C ( NHAr ) CMe  N ( Ar ) + Cl − in which the dab ligand has undergone CH activation at one of methyl groups of the dab bridge. The CH cleavage reaction is reversible in the sense that thermally, the cyclometalated Ir complex decomposes to regenerate the free ligand.

Palladium-mediated carbosubstitutions in spiranes

Abstract Carbosubstitutions in spirene triflates can be effected by Pd-catalyzed couplings with stannylated or zincated arenes. Differential carbosubstitution resulted from stepwise triflation and coupling in spiro[4,4]-nonane-1,6-dione. Catalytic hydrogenation of the 1,6-diphenyl-1,6-diene gave the cis,cis-disubstituted spirane. Metal hydride reduction of intermediate monoketone gave mainly the cis-alcohol.

Substituent crowding in nitrobenzenes

Abstract The rotational motion of adjacent nitro groups in 1,2-dinitrobenzene and 1,2,4-trinitrobenzene has been investigated using X-ray diffraction and quantum chemical calculations. Pilot calculations on nitrobenzene indicate that density functional theory provides reliable geometries for this type of compound. Using this method for the substituted compounds, we find that rotation of the two adjacent nitro groups can take place quite freely within a groove in the potential surface that defines an interlocking cogwheel mode. The experimental structures of both molecules are found to have nitro group configurations corresponding to this mode of motion.

The ternary system AuCoSn and the crystal structure of AuCo2(1−a)Sn4

Abstract The phase relations in the ternary system AuCoS have been studied by powder X-ray diffraction, metallography, electron microprobe analysis, and thermal analysis. The condensed phases occurring, tie-lines and tie-triangles are presented for an isothermal section of the phase diagram at 380°C. A hitherto unknown genuine ternary phase AuCo2(1−a)Sn4 is found, with 0.167 ⩽ u ⩽ 0.180, and as indicated by the formula, the non-stoichiometry is of the subtractional kind (confirmed by density measurements). The unit cell is monoclinic (space group C2/m) with a = 1260.3(3), b = 421.3(1), c = 522.9(1) pm and β = 104.62(2)° for u = 0.167. Au in 2a: (0.833) Co, Sn(I) and Sn(II) in 4i with x = 0.2116(2), z = 0.3331(5) for Co, x = 0.41759(9), z = 0.6493(2) for Sn(I) and x = 0.18489(9), z = 0.8142(2) for Sn(II). The structure of AuCo2(1−a)Sn4 is of the Ni3−xSn4 type and its atomic arrangement is discussed in relation to that of the prototype. AuCo2(1−a)Sn4 behaves as a virtually ideal Curie paramagnet with μp = 1.191(3) μu per Co atom.

Palladium mediated substitutions and rearrangements in spiro[4,4]nonanes

Abstract The two-step NaBH 4 CeCl 3 1,2-reduction of spiro[4,4]nonane-2,7-diene-1,6-dione gave a rans-alcohol as a first product which reacted further to the corresponding cis,trans-diol. Pd(II)-catalysis was used to effect an allylic rearrangement from the 1,6-diacetate to the corresponding 2,7-diacetate. Both diacetates were substrates for Pd(0)-catalyzed allylic alkylations. The relative stereochemistry was retained.

SYNTHESIS OF CYCLIC CONSTRAINED β-OXO-SUBSTITUTED α-AMINO ACIDS

ABSTRACT Ru(II)-catalyzed RCM reaction with a 5,5-diene of (2R)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine provided a spiroannulated cyclohexenone as substrate for conjugate additions of organocuprates. Acid hydrolysis gave β-oxo-substituted α-amino acids. Assignments of configurations are based on single crystal X-ray analyses.