Louis Denner

Synthesis of 2-(2-oxopyrrolidin-1-yl)-1,4-quinones and a hydrogen-bonded 2-alkylamino-1,4-naphthoquinone

Abstract Oxidation of four 1-(2,5-(dimethoxyaryl)pyrrolidin-2-ones with silver(II) oxide in acidic medium gave the corresponding quinones in moderate to good yield. 1,4-Naphthoquinone and 2-methoxy- Δ1-pyrroline reacted in methanol to give 2-(3-methoxycarbonylpropylamino)-1,4-naphthoquinone [16], the structure and hydrogen bonding characteristics of which were determined by X-ray crystallography.

The crystal and molecular structure of [(η5-C5H5)Fe(CO)2Re(CO)5] and the reactions of [(η5-C9H7)Fe(CO)2Re(CO)5] with RNC (R = t-Bu, 2,6-Me2C6H3)

Abstract The crystal structure determination of [(η5-C5H5)Fe(CO)2Re(CO)5] (1) is reported (space group P21/c, a = 27.737(5), b = 6.922(5), c = 14.654(4) A, β = 98.17(2)°). Final R and Rw values were 0.031 and 0.026 (w=k/σ2(F)). The non-bridged FeRe bond length is normal (2.888(1) A, average value) and the FeReC(O) (equatorial CO) angles varied between 74° and 99° with an equatorial CO group bending in towards the cyclopentadienyl ligand. The FeReC(O) axial angle (167°) of one of the independent molecules of 1 differs markedly from 180°. This CO ligand is, however, almost perpendicular to the plane of the equatorial CO ligands on Re. The synthesis and characterization of [(η5-C9H7)Fe(CO)2Re(CO)5] and its reactions with RNC (R = t-Bu, 2,6-Me2C6H3) are also reported. In all the reactions studied the products [(η5-C9H7)FeRe(CO)7−x(CNR)x] (x=1−3) were characterized and revealed substitution only on the Re atom. The attempted crystal structure determination of the unsubstituted dimer complex (twinned crystal) is also described.

Reaction of 3,4-dimethyl-1-oxa-6,6aλ4-diselena-2-azapentalene with tetraphosphorus decasulphide: a new molecular rearrangement. X-Ray crystal structures of 3,4-dimethyl-1-oxa-6,6aλ4-diselena-2-azapentalene, 2,4-dimethyl-1-thia-6,6aλ4-diselena-3-azapentalene, and 2,4-dimethyl-1,6-dithia-6aλ4-selena-3-azapentalene

The title compound (1) reacts with tetraphosphorus decasulphide to give two molecular rearrangement products (2) and (3), together with compound (4); the structures of compounds (1)–(3) have been established by X-ray single crystal analyses.

Crystal and molecular structure of bis (μ-chloro)bis[chloro(1,1′-dimethyl-2,2′-diimidazolylsulfide)copper(II)]

The title compound is prepared from 1-methylimidazoline-2(3H)-thione (mimtH) and copper(II) chloride, in a 1∶1 mole ratio in methanol. The crystals are monoclinic, space groupP21/n, witha=8.530(2),b=14.258(2),c=9.693(2) Å,β=93.15(2)°,Z=2. The molecular structure shows a dimeric copper(II) complex, in which each copper is chelated by a 1,1′-dimethyl-2,2′-diimidazolylsulfide ligand, and bonded to three chlorine atoms, two bridging and one terminal. The coordination geometry of each copper is approximately square pyramidal, with two nitrogen atoms, a terminal chlorine, and one of the bridging chlorines forming the square plane. The second bridging chlorine forms the apex of the pyramid.

Crystallographic study of restricted rotation ino-formanilides

The crystal structures ofcis- andtrans-o-methylformanilide, of itscis-thio analogue, and oftrans-o-phenylformanilide have been studied with a view to clarifying the anomalously high barrier to rotation of the carbonyl group. The pair of resolved geometrical isomers is shown to be stabilized in the solid state primarily by hydrogen bonding. The increased barrier to rotation is inferred not to arise from mesomeric involvement of the carbonyl group, but from nuclear screening by the nitrogen lone pair.

Substituted cyclopentadienyl complexes. 5. Crystal and molecular structure of [(η5-C5H4Me)Fe(CO)(L)I] [L = 2,6-Me2C6H3NC, P(OMe)3, and P(C6H11)3]

The crystal and molecular structures of three derivatives of [(η5-C5H4Me)Fe(CO)(L)I] [L=2,6-Me2C6H3NC, P(OMe)3, and P(C6H11)3] have been determined. [(η5-C5H4Me)Fe(CO)(CNC6H3Me2-2,6)I] (1): Space groupP¯1,Z=2,a=13.193(7),b=8.183(5),c=7.465(4) Å,α=95.13(5),β=94.39(5), γ=91.09(5)°. [(η5-C5H4Me)Fe(CO)[P(OMe)3]I] (2): Space groupP21/c,Z=4,a=7.296(3),b=24.471(6),c=8.877(3) Å,β=111.92(4)°. [(η5-C5H4Me)Fe(CO)[P(C6H11)3]I] (3): Space groupP21/c,Z=4,a=9.809(3),b=14.147(2),c=8.276(3) Å,β=103.07(2)°. The structures were refined toR values of 0.045, 0.070, and 0.061, respectively. Disorder was observed in the P(OMe)3 ligands on2. Structural data for1 and3 reveal (i) a small movement of the Fe atom away from the ringC atom containing the methyl group, (ii) a larger movement of ring C atoms away from the ring least-squares plane for3 than for1, and (iii) a shift toward an allyl-ene bond length variation in the ring distances for3. Molecular mechanics calculations performed on2 produce a low-energy conformation similar to that found in the crystal structure determination of2 with an energy barrier to ring rotation of ±5 kcal mol−1. A correlation of the structural and molecular mechanics data with the nmr spectra of complexes1 to3 indicates that the steric influence ofL on the ring rotation could be due to ring distortion and/or interaction with the ring methyl group.

Rotamers and isomers in the fulgide series. Part 2. Stereochemistry and conformational analysis of bis-(p-methoxybenzylidene)succinic anhydrides by X-ray crystallography and molecular mechanics

Conformational analysis of bis-(3,4-dimethoxybenzylidene)succinic anhydride suggests that in addition to a Z,Z-isomer, the E,E-isomer of this diarylfulgide occurs as three distinct relatively freely interconvertible chiral rotamers and their enantiomers. The E,E-isomer undergoes facile dehydrogenation to form an arylnaphthalene derivative. Crystals were obtained of a symmetrical E,E-rotamer in two forms, the Z,Z-isomer and the arylnaphthalene derivative. X-Ray structures of these crystalline forms are reported. The conformations of the other rotamers were simulated by molecular mechanics, using an empirical force-field based on the observed structure of the symmetrical E,E-rotamer, described here. The aromatic rings of the E,E-isomers are eclipsed and under severe strain, which inhibits free rotation. Packing energy promotes the crystallization of one of the possible E,E-rotamers only and has a marked effect on the orientation of the methoxy substituents.

Crystal structure and absolute configuration of (–)-3-O-acetyl-6-bromo-3′,4′,5,7-tetra-O-methylepicatechin, a reference compound for the aromatic bonding positions of 2,3-cis-procyanidins

Determination of the structure of (–)-(2R,3R)-3-O-acetyl-6-bromo-3′,4′,5,7-tetra-O-methylepicatechin in the crystalline state confirmed the position of bromination and hence that of its 8-bromo isomer; both are key reference compounds for assessing the aromatic bonding positions in 2,3-cis-procyanidins. The half-chair conformation of the heterocyclic ring is shown to be in close agreement with the published structure of (–)-epicatechin. Determination of the absolute configuration of the derivative, in accord with earlier chemical evidence, is shown to hinge on detailed refinement of an extended data set.

Crystal structure of 1-(o-tolyl)-naphthalene

Abstract1-(o-Tolyl)-naphthalene was obtained in the synthesis of the 1,8-disubstituted analogue. Crystallographic analysis established orthogonal alignment of the ring systems, in agreement with calculations to investigate the existence of rotamers due to restricted rotation.

Intramolecular, two-substituent, consecutive and sequential (conseq) migrations: X-ray structure of an indeno[1,2,3-de]quinoline product

Abstract Evidence, including the X-ray structure verification of a crucial reaction product, is presented in support of the postulation that intramolecular, two-substituent, consecutive and sequential migrations accompany the formation of certain indeno[1,2,3- de ]quinolinones.