24401-44-3Relevant academic research and scientific papers
Transformation of Amides into Highly Functionalized Triazolines
Slagbrand, Tove,Volkov, Alexey,Trillo, Paz,Tinnis, Fredrik,Adolfsson, Hans
, p. 1771 - 1775 (2017/08/09)
Triazoles and triazolines are important classes of heterocyclic compounds known to exhibit biological activity. Significant focus has been given to the development of synthetic approaches for the preparation of triazoles, and they are today easily obtainable through a large variety of protocols. The number of synthetic procedures for the formation of triazolines, on the other hand, is limited and further research in this field is required. The protocol presented here gives access to a broad scope of 1,4,5-substituted 1,2,3-triazolines through a one-pot transformation of carboxamides. The two-step procedure involves a Mo(CO)6-catalyzed reduction of tertiary amides to afford the corresponding enamines, followed by in situ cycloaddition of organic azides to form triazolines. The amide reduction is chemoselective and allows for a wide variety of functional groups such as esters, ketones, aldehydes, and imines to be tolerated. Furthermore, a modification of this one-pot procedure gives access to the corresponding triazoles. The chemically stable amide functionality is demonstrated to be an efficient synthetic handle for the formation of highly substituted triazolines or triazoles.
Hydroaminomethylation of styrene catalyzed by rhodium complexes containing chiral diphosphine ligands and mechanistic studies: Why is there a lack of asymmetric induction?
Crozet, Delphine,Kefalidis, Christos E.,Urrutigoity, Martine,Maron, Laurent,Kalck, Philippe
, p. 435 - 447 (2014/03/21)
Various chiral diphosphine ligands (P-P) have been introduced in the coordination sphere of neutral or cationic rhodium complexes, and the generated species catalyze efficiently the hydroaminomethylation reaction of styrene with piperidine. The diphospholane ligand family is particularly adapted to this tandem reaction leading to the branched amine with good chemo- and regioselectivity. We analyzed in detail the main reasons why the reaction proceeds with no enantioselectivity. Catalytic and HP-NMR experiments reveal the presence of the [Rh(H)(CO)2(P-P)] species as the resting state. DFT calculations allow us to elucidate the mechanism of the hydrogenation of the branched (Z) or (E)-enamine. From the [Rh(H)(CO)(P-P)] active species, the coordination of the two enamine isomers, the hydride transfer, the H2 activation, and then the final reductive elimination follow similar energetic pathways, explaining the lack of enantioselectivity for the present substrates. Analysis of the energy-demanding steps highlights the formation of the active species as crucial for this rate-limiting hydrogenation reaction.
Calix[4]arene-diphosphite rhodium complexes in solvent-free hydroaminovinylation of olefins
Monnereau, Laure,Semeril, David,Matt, Dominique
supporting information; experimental part, p. 1670 - 1673 (2010/12/24)
Under solvent-free conditions rhodium complexes containing hemispherical diphosphites based on a calix[4]arene skeleton catalyse efficiently the hydroaminovinylation of α-olefins, thereby leading to high proportions of linear enamines/amines (when startin
Highly regioselective hydroformylation with hemispherical chelators
Semeril, David,Matt, Dominique,Toupet, Loic
experimental part, p. 7144 - 7155 (2009/08/07)
The hemispherical diphosphites (R,R)- or (S,S)-5,11,17,23-tetratert-butyl- 25,27-di(OR)-26,28-bis(1,1′-binaphthyl-2,2′-dioxyphosphanyloxy) -calix[4]arene (R = OPr, OCH2Ph, OCH2-naphtyl, O-fluorenyl; R = H, R' = OPr) (LR), all with C2 symmetry, have been synthesised starting from the appropriate di-O-alkylated calix[4]-arene precursor. In the presence of [Rh(acac)(CO)2], these ligands straightforwardly provide chelate complexes in which the metal centre sits in a molecular pocket defined by two naphthyl planes related by the C 2 axis and the two apically situated R groups. Hydroformylation of octene with the LPr/Rh system turned out to be highly regioselective, the linear-to-branched (l:b) aldehyde ratio reaching 58:1. The l:b ratio significantly increased when the propyl groups were replaced by -CH 2Ph (l:b = 80) or -CH2naphthyl (1:b = 100) groups, that is, with substituents able to sterically interact with the apical metal sites, but without inducing an opening of the cleft nesting the catalytic centre. The trend to preferentially form the aldehyde the shape of which fits with the shape of the catalytic pocket was further confirmed in the hydroformylation of styrene, for which, in contrast to catalysis with conventional diphosphanes, the linear aldehyde was the major product (up to ca. 75 % linear aldehyde). In the hydroformylation of frarts-2-octene with the Lbenzyl/ Rh system, combined isomerisation/hydroformylation led to a remarkably high 1:b aldehyde ratios of 25, thus showing that isomerisation is more effective than hydroformylation. Unusually large amounts of linear products were also observed with all the above diphosphites in the tandem hydroformylation/amination of styrene (1:b of ca. 3:1) as well as in the hydroformylation of allyl benzyl ether (1:b ratio up to 20).
Highly Selective Synthesis of Enamines from Olefins
Ahmed, Moballigh,Seayad, Abdul Majeed,Jackstell, Ralf,Beller, Matthias
, p. 5615 - 5619 (2007/10/03)
Astonishing chemoselectivity is observed in the rhodium-catalyzed formation of enamines from olefins, CO, H2, and amines (see scheme). This new reaction can be used with a broad range of substrates and is high-yielding and highly selective (n/iso = 99:1 in most cases).
