- Dormant versus evolving aminopalladated intermediates: Toward a unified mechanistic scenario in PdII-catalyzed aminations
-
PdII-catalyzed alkene aminopalladation and allylic Ci£H activation are two competing reaction sequences sharing the same reaction conditions. This study aimed at understanding the factors that bias one or the other path in the intramolecular oxidative cyclization of two types of N-tosyl amidoalkenes. The results obtained are in accord with the initial generation of a high-energy cyclic (5- or 6-membered) aminopalladated intermediate. However, this latter species can evolve only if the following specific conditions are met: the availability of distocyclic β-H elimination pathway, the presence of a strong terminal oxidant, or the availability of a carbopalladation pathway. Conversely, the cyclic alkylpalladium complex is only a latent species in equilibrium with the initial substrate and cannot evolve. Such a reactivity hurdle leaves the way open for alternative reactivities such as allylic Ci£H activation of the olefinic substrate to generate a η3-allyl complex followed by its interception by the nitrogen nucleophile, [3,3]-sigmatropic rearrangement, or decomposition. This study proposes a unifying mechanistic picture that connects these competing mechanisms. Asleep or awake? Unsaturated N nucleophiles react through two competing pathways under PdII catalysis: Ci£H allylic activation and aminopalladation. New data are in accord with the initial generation of a high-energy cyclic aminopalladated intermediate (API) that can either evolve along different pathways such as β-H elimination, oxidation, or carbopalladation, or lay dormant, the latter leading to alternative types of reactivity, such as allylic Ci£H activation or [3,3]-sigmatropic rearrangement, gaining the upper hand (see scheme; Ts=p-toluenesulfonyl). Copyright
- Rajabi, Jamshid,Lorion, Melanie M.,Ly, Vu Linh,Liron, Frederic,Oble, Julie,Prestat, Guillaume,Poli, Giovanni
-
supporting information
p. 1539 - 1546
(2014/03/21)
-
- Stoichiometric and catalytic cross dimerization between conjugated dienes and conjugated carbonyls by a ruthenium(0) complex: Straightforward access to unsaturated carbonyl compounds by an oxidative coupling mechanism
-
A series of stoichiometric and catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are studied. The reaction of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with methyl acrylate gives a Ru(0) complex, Ru[methyl η4-cisoid- (2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa) in 97% yield. Similar treatments of 2a with a series of tert-butyl acrylate, methyl crotonate, 3-buten-2-one, and N,N-dimethylacrylamide produce similar analogues of 3ac. When (E)-1,3-pentadiene complex 2d is employed in the reaction with methyl acrylate, the branched coupling product Ru[methyl η4- cisoid-(2E,4E)-4-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-b) is dominantly obtained in 65% yield along with the linear product in 19% yield. In the case of the (E)-2,5-dimethylhexa-1,3-diene complex 2e, the corresponding branch product is exclusively obtained in 86% yield. The catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are established by 2. The origin of the present chemoselectivity is the η4-coordination of a conjugated diene and η2- coordination of an electron-deficient alkene to formal 6e coordination sites at Ru(0), and the regioselectivity being prone to giving branched products is interpreted as an oxidative coupling mechanism, involving nucleophilic attack of the coordinated diene to the coordinated electron-deficient alkene.
- Hirano, Masafumi,Arai, Yasutomo,Hamamura, Yuka,Komine, Nobuyuki,Komiya, Sanshiro
-
experimental part
p. 4006 - 4019
(2012/07/13)
-
- Stoichiometric and catalytic cross dimerization between butadiene and methyl acrylate promoted by a Ruthenium(0) complex
-
Treatment of Ru(η4-butadiene)(η4-1,5-COD) (NCMe) (1a) with methyl acrylate in benzene for 3 h at 6 °C produces Ru{cisoid-η4-(2E,4E)-(methyl hepta-2,4-dienoate)} (η4-1,5-COD)(NCMe) (2a) in 97% yield. Complex 1a (2 mol %) catalyzes the chemoselective cross dimerization between butadiene and methyl acrylate in benzene to give a mixture of the regioisomers of methyl heptadienoate in 43% yield by the oxidative coupling reaction.
- Hirano, Masafumi,Arai, Yasutomo,Komine, Nobuyuki,Komiya, Sanshiro
-
scheme or table
p. 5741 - 5743
(2011/02/23)
-
- Asymmetric total synthesis of sperabillins B and D via lithium amide conjugate addition
-
Diastereoselective conjugate addition of homochiral lithium (R)-N-allyl-N-α-methylbenzylamide to methyl (2E,5E)-hepatadienoate, followed by protecting group manipulation and subsequent iodocyclocarbamation allows a concise route to the core fragment, methyl (3R,5R,6R)-3,6-diamino-5- hydroxyheptanoate, of sperabillins B and D. Differentiation between the C-3 and C-6 primary amino groups of this core amino acid was readily achieved by treatment with acetone, giving the 5,6-isopropylidene and C-3-imine protected diamine, with subsequent regioselective acylation of the C-6-nitrogen facilitating the total synthesis of sperabillin D in 10.8% overall yield, and the first asymmetric synthesis of sperabillin B in 5.8% overall yield.
- Davies, Stephen G.,Haggitt, Jane R.,Ichihara, Osamu,Kelly, Richard J.,Leech, Michael A.,Mortimer, Anne J. Price,Roberts, Paul M.,Smith, Andrew D.
-
p. 2630 - 2649
(2007/10/03)
-
- Total asymmetric synthesis of sperabillins B and D
-
A consise route to the core fragment of sperabillins B and D, methyl (3R,5R,6R)-3,6-diamino-5-hydroxyheptanoate, has been developed with a subsequent novel protection strategy allowing the total asymmetric synthesis of sperabillins B and D.
- Davies, Stephen G.,Kelly, Richard J.,Mortimer, Anne J. Price
-
p. 2132 - 2133
(2007/10/03)
-
- Cobalt mediated alkene/diene coupling; documentation of scope, limitations, and regioselectivity
-
The cobalt hydride catalyzed addition of alkenes bearing electron withdrawing groups to methylated 1,3-butadienes leads to functionalized hexadiene products.The reaction is limited to addends featuring at least one terminal alkene moiety.
- Feldman, Ken S.,Grega, Kevin C.
-
p. 251 - 260
(2007/10/02)
-
- Co-dimerisation of 1,3-Dienes and Acrylic Esters catalysed by Cationic Allylpalladium Complexes: the Role of Phosphines
-
Basic phosphines, especially tributylphosphine, when added in 1:1 ratio to cationic allylpalladium complexes, allow the selective co-dimerisation of 1,3-dienes and acrylic esters to linear, unsaturated esters, presumably owing to the inducement of an η3-η1 shift of the allyl ligands by the phosphines.
- Grenouillet, Pierre,Neibecker, Denis,Tkatchenko, Igor
-
p. 542 - 543
(2007/10/02)
-
- SYNTHESIS OF 8E,10E-DODECADIEN-1-OL FROM METHYL 2,5-HEPTADIENOATES
-
A method is proposed for the synthesis of 8E,10E-dodecadien-1-ol (the pheromone of the codling moth) from methyl 2Z,5E-heptadienoate and from a mixture of 2E,5Z- and 2Z,5Z-heptadienoic esters.Prototropic isomerization of the methyl esters of the 2Z,5E- and of the mixture of 2E,5Z- and 2Z,5Z-heptadienoic acids takes place quantitatively with the formation of methyl 3E,5E-heptadienoate and methyl 3E,5Z-heptadienoate respectively.
- Zakharkin, L. I.,Babich, S. A.
-
p. 1995 - 2000
(2007/10/02)
-