Hydride compounds trans configuration

The addition of nitrosyl chloride to cyclohexene in sulfur dioxide at low temperature21 -25, or the reaction of cyclohexene with 3-methylbutyl nitrite and hydrochloric acid (producing nitrosyl chloride in situ)25 gave only the tram-adduct 1, isolated in high yield as a crystalline nitroso dimer (azodioxy compound) with E configuration at the N—N double bond. The trans configuration of the chloro and nitroso groups (mixture of diaxial and diequatorial conform-ers) was deduced by IR and H-NMR analyses (a mixture of conformers with both axial and both equatorial substituents is apparent)23-25 and by reduction with lithium aluminum hydride in tetrahydrofuran to yield tram-2-chloro-l-cyclohexanamine (trans-2)23. 

Additionally, MO calculations indicate the lowest energy orientation occurs with the three strongest trans-influence ligands (two hydrides and a PPh3) in a facial configuration. Calculations on compounds IrX(CO)(PR3)2 indicates that weak donors X and strong 7r-acceptors PR3 favour addition in the XIrCO plane [134, 135],... 

There have a number of computational studies of hypothetical RMMR species [10-13, 40, 411. The simplest compounds are the hydrides HMMH. Some calculated structural parameters and energies of the linear and trans-bent metal-metal bonded forms of the hydrides are given in Table 1. It can be seen that in each case the frans-bent structure is lower in energy than the linear configuration. However, these structures represent stationary points on the potential energy surface, and are not the most stable forms. There also exist mono-bridged, vinylidene or doubly bridged isomers as shown in Fig. 2... 

The oxidation of substituted dicarbonyl complexes of chromium(I) featuring the bidentate ligands dppm and dppe has been examined. Chromium(O) starting materials, Cr(CO)2(dppm)2 and Cr(CO)2(dppe)2, both with cis carbonyl configurations, were oxidized to trans cations [Cr(CO)2(dppm)2]+ and [Cr(CO)2(dppe)2]" chemical and electrochemical methods were employed. Chemical oxidation of the dppm compound proved more facile than that of the dppe analogue this had been predicted on the basis of electrochemical studies. The dicarbonyl hydride, [Cr (CO)2(dppm)2H]+, was isolated from the oxidation reaction of [Cr(CO)2(dppm)2] with O2/HCIO4, while the same reaction conditions oxidized the neutral dppe complex to the cation. 

Oxidative addition [1, 38] of 1-alkenyl, 1-alkynyl, allyl, benzyl, and aryl halides to a palladium(O) complex affords a stable trans-o-p al 1 adi u m( 11) complex (11). The reaction proceeds with complete retention of configuration for alkenyl halides and with inversion for allylic and benzylic halides. Alkyl halides having /5-hydrogens are rarely useful because the oxidative addition step is very slow and may compete with /5-hydride elimination from the <7-organopalladium(II) species. However, it has been recendy shown that iodoalkanes undergo the cross-coupling reaction with organoboron compounds (Section 2.4.5). 

Reduction of the ketolactam 390 (having the newly assigned A/B trans stereochemistry) with sodium borohydride followed by reduction of the amide with lithium aluminum hydride gave an amino alcohol. Oxidation of this amino alcohol with chromic acid followed by rereduction with lithium aluminum hydride gave an amino alcohol different from that obtained previously. In the oxidation to the ketone 373, therefore, epimerization at C-9a must have occurred, and the two amine alcohols must have the configurations 391 and 392. Since in both compounds Bohlmann bonds were observed in the IR spectrum, the A/ ring juncture is trans. 

The synthesis of 8-aza-D-homoestrogens has also been carried out from compound (432) (Scheme 42) [551, 552]. Compound (432) was converted via (435) in four stages into the isoquinoline derivative (438). The action of thionyl chloride led to the chloride (439), which, on reaction with 2,4-dim ethoxy-.1,4-cyclohexadiene, gave the tricyclic compound (440). Acid hydrolysis of this compound was accompanied by cyclization to the D-homo derivative (443). Reduction of the latter with lithium aluminum hydride gave a mixture of equal amounts of the cis-C/D ketone (441) and the trans-C/D ketone (442) the first was isomerized into the second on treatment with sodium methoxide. The configuration of compounds (441)-(443) at Cg has remained undetermined. 

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