PtBr2/nBu4PBr (without solvent) or K2PtCl4/NaBr (in water) have been shown to efficiently catalyze the hydroamination of ethylene by aniline and are poor catalysts for the hydroamination of ethylene by diethylamine. A DFT study on the hydroamination mechanism indicates that the energetic span of the C2H4/Et2NH catalytic cycle is close to that of the C2H4/PhNH2 cycle. The poor performance is attributed to rapid catalyst degradation with reduction to metallic platinum. Pt0, on the other hand, catalyzes a transalkylation process, partially transforming Et2NH into Et3N, EtNH2 and NH3. This process is inhibited by C2H4. Mechanistic considerations for the Pt0‐catalyzed transalkylation process are presented.

To use carbon dioxide as a source of carbon, recent progress has been made toward the synthesis of higher value chemicals and in particular toward Cn compounds. In this context, we report here the synthesis of a borylated C3‐carbohydrate from CO2 as the only source of carbon. This result corresponds to the unprecedented formation of a polyol chain and of asymmetric carbon atoms from CO2. The adopted strategy involves the Fe‐catalysed selective 4e− reduction of CO2 into bis(boryl)acetal followed in one‐pot by a carbene‐mediated C−C coupling reaction. Boron is shown to play a key role in the coupling step enabling to observe the first diastereoselective formose‐type reaction. This result is in addition obtained under mild reaction conditions (T<80 °C, 1 atm of CO2) and short reaction time (t<2 h).

The thermal properties of Cp*W(NO)(H)(η 3 -CH 2 CHCMe 2 ) (1), Cp*W(NO)(H)(η 3 -CH 2 CHCHPh) (2), and Cp*W(NO)(H)(η 3 -CH 2 CHCHMe) (3) (Cp* = η 5 -C 5 Me 5 ) have been investigated. Thermolyses of 1−3 in n-pentane lead to the loss of the original allyl ligand and the formation of the same mixture of isomeric products, namely, Cp*W(NO)(H)(η 3 -CH 2 CHCHEt) (4a) and Cp*W(NO)(H)(η 3 -MeCHCHCHMe) (4b) and their coordination isomers. Similarly, 1 reacts with cyclohexane and n-heptane to form Cp*W(NO)(H)(η 3 -C 6 H 9 ) and isomers of Cp*W(NO)(H)(η 3 -C 7 H 13 ), respectively. It is likely that complexes 1−3 first effect the selective, single-terminal C−H activation of the linear alkanes, but the first-formed products are thermally unstable and undergo two additional successive C−H activations to form the final allyl complexes. Consistent with this view is the fact that a bis(alkyl) intermediate complex can be trapped with N-methylmorpholine. Thus, the thermolysis of 1 in Nmethylmorpholine affords a single organometallic complex, Cp*W(NO)(η 2 -CH 2 NC 4 H 8 O)(η 1 -CH 2 CH 2 CHMe 2 ) (7). Complexes 2 and 3 react with N-methylmorpholine in an identical manner. Finally, 1 effects the multiple C−H activations of 1-chloropropane and 1-chlorobutane and forms the corresponding Cp*W(NO)(Cl)(η 3 -allyl) complexes. All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them have been established by single-crystal X-ray crystallographic analyses.

The preparation of optically active lactams from 3‐aryl‐2‐piperidinone is reported. The quaternary carbon stereocentres were formed using palladium‐catalysed asymmetric allylic alkylation reactions. The resulting enantioenriched compounds are useful intermediates for the synthesis and development of neurokinin antagonists.

A DFT/B3LYP study with inclusion of solvent and temperature effects has probed the olefin activation mechanism for the intermolecular hydroamination of ethylene and 1-hexene by aniline derivatives catalyzed by the PtX2/X– system on the basis of a variety of experimental results, including new experiments on catalyst deactivation. For ethylene and aniline, the calculated ΔG ‡ cycle between the resting state [PtX3(C2H4)]−, 1 X , and the TOF-determining transition state of the C–H reductive elimination from [PtX3(H)(CH2CH2NHPh)]−, TS2 X , is slightly smaller for X = Br than for Cl or I. The ΔG ‡ cycle decreases as the aniline basicity decreases. For the slightly less efficient hydroamination of 1-hexene, ΔG ‡ cycle is greater than that for the hydroamination of ethylene, with a preference for the Markovnikov addition, in agreement with experiment and with essentially equivalent ΔG ‡ cycle values for the Br and I systems. In general, the results of the calculations are in agreement with the experimental observation. A clear-cut comparison of trends is hampered by the small energy differences and by the possibility, proven in certain cases, that the reaction parameters under investigation affect the catalyst degradation rate in addition to its intrinsic activity. Extrapolation of the computational study to the fluoride system suggests that this should be even more active. However, experimental studies show that this is not the case. The reason for this anomaly has been traced to the basicity of the fluoride ion, which triggers more rapid catalyst decomposition. A bonding analysis of 1 X indicates a significant push–pull π interaction between the C2H4 and the trans-F ligand.

A study of the addition of nucleophilic reagents that are also strong Brønsted bases (Et3N, pyridine, quinuclidine, MeO -) to nBu4P + [PtBr3(C2H4)] -(1) and trans-[PtBr2(NHEt2)(C2H4)] (7) has provided key information on the deactivation of the hydroamination PtBr2/Brcatalyst, leading to metallic platinum. The addition of NEt3 to 1 in CD2Cl2 is reversible and temperature dependent; the quantitative formation of the zwitterionic complex trans-[Pt (-) Br2( NEt3)-(CH2CH2N (+) Et3)] ( 9) is observed only at low temperature whereas slow deposition of metallic platinum occurs at room temperature. The addition of NEt3 to 7 in CD2Cl2 is also reversible and temperature dependent, yielding trans-[Pt (-) Br2(NHEt2)(CH2CH2N (+) Et3)] (10) quantitatively at low temperature. At room temperature, this reaction led to the deposition of metallic platinum and to the formation of a complex identified as trans-[PtBr2(NHEt2)(CH2CHNEt2)] (11). The carbyl ligand in 11 is shown by an X-ray structural study to be in-between the π-bonded enamine and the σ-bonded iminiumalkyl configurations. The addition of MeONa to 7 results in the formation of the same products 11 and Pt 0 . On the basis of these results, a mechanism for the base-induced decomposition of Pt II (C2H4) complexes that involves Wacker-type β-H elimination followed by intermolecular hydride transfer, ligand rearrangements and final deprotonation is proposed. Addition of more nucleophilic N-based ligands (pyridine, quinuclidine) to 7 ultimately leads to C2H4 and Et2NH substitution rather than to metal reduction, even though evidence for a kinetically controlled nucleophilic addition to the coordinated ethylene is given by the quinuclidine system. From the reaction with pyridine, complex cis-PtBr2(py)2 was isolated and structurally characterized.

to the highest catalytic activity for the intermolecular hydroamination of ethylene, 1-butene, and 1-hexene with aniline-type amines. Excellent activities were also found using Rh I Wilkinson's catalysts and the very efficient "in-situ generated" I from PPh 3 /I 2 , which can substitute pre-synthesized nBu 4 PI (see scheme; CE=catalytic efficiency). halides hydroamination non-activated alkenes phosphines rhodium The catalytic system RhCl 3 •3H 2 O/2P(p-CH 3 C 6 H 4 ) 3 /65nBu 4 PI/2I 2 , which was discovered recently in our research group, allows the highest catalytic activity ever reported for the intermolecular hydroamination of ethylene, 1-butene, and 1-hexene with aniline-type amines (0.3^^mol^% catalytic precursor) to give the expected N-alkyl-(N-ethyl-, 1) and N,N-dialkylanilines (N,N-diethyl-, 2), along with 2-methyl quinolines (3) (in the case of ethylene). The effects of time and temperature, as well as the nature of the phosphonium salt, phosphine, and amine on the catalytic activity of this reaction have been studied. This system is particularly efficient for the hydroamination of ethylene with aniline in the presence of 2,2'bis(diphenylphosphino)-1,1'-binaphthyl (CE*=460) and tri(p-tolyl)phosphine (CE*=520).Good to excellent activities were also found by combining Wilkinson's catalysts (Rh I complexes) with nBu 4 PI and I 2 . The simple association of PPh 3 and I 2 has been shown to be a very efficient "in-situ generated" source of I promoters. *CE (catalytic efficiency)=TON 1 +2TON 2 +2TON 3 .

α‐carbonyl homoallylic alcohols have been synthesized in a one‐pot reaction from benzaldehyde and allylic alcohols. The nickel‐catalyzed allylation of α‐hydroxyketones has first been studied and allowed the identification of Ni(cod)2/dppf as the most suitable catalytic system. The tandem reaction that combines the benzoin condensation of aldehydes (synthesis of α‐hydroxyketones) promoted by the 1,3‐dimethylimidazolium chloride/DBU system and the nickel‐catalyzed allylic alkylation with allylic alcohol has been realized in EtOH as green solvent. The reaction is 100 % atom‐economical and water is formed as sole by‐product. A broad scope of different benzaldehyde derivatives as well as various allylic alcohols is also described.