Asymmetric catalysis Heck reactions

For recent reviews of the asymmetric Heck reaction, see (a) Shibasaki, M., Boden, C.D.J. and Kojima, A. (1997) The asymmetric Heck reaction. Tetrahedron, 53, 7371-95 (b) Shibasaki, M. and Vogl, E.M. (1999) Heck reaction, in Comprehensive Asymmetric Catalysis, Vol. 2 (eds E.N. Jacobsen, A. Pfaltz and H. Yamamoto), Springer, Berlin, pp. 457-87 (c) Donde, Y. and Overman, L.E. (2000) Asymmetric intramolecular Heck reactions, in Catalytic Asymmetric Synthesis (ed. I. Ojima), WUey-VCH Verlag GmbH, New York, pp. 675-97 (d) Dounay, A.B. and Overman, L.E. (2003) The as5mmetric intramolecular Heck reaction in natural product total synthesis. Chem. Rev., 103, 2945-64 (e) Shibasaki, M., Vogl, E.M. and Ohshima, T. (2004) Asymmetric Heck reaction. Adv. Synth. Catal., 346,1533-52. 

Asymmetrically induced Heck reactions can also be performed with substrates containing two enantiotopic leaving groups. Starting from dimedone, novel cyclohexa-l,4-diene-l,5-diol bis(nonafluorobutanesulfonates) such as 309 have been prepared and cycUzed under palladium catalysis to cleanly give bicy-clo[4.2.0]octadienes 370 and bicyclo[4.2.0]octenones, respectively, by an unprecedented 4-exo-trig process (Scheme 8.77, cf. Scheme 8.66). In the presence of a chiral phosphine ligand, the products could be obtained with modest enantiomeric excesses (up to 52% ee) [239]. 

Pd complexes 9-12 were tested for their catalytic behavior in the asymmetric Heck reaction involving the phenylation of 2,3-dihydrofuran (Scheme 3). The results are summarized in Table 2. The two isomeric products of 2-phenyl-2,5-dihydrofuran are formed with varying yields from 80% to 0%. The obtained ee s are high. Complex 12 is shown to be catalytically inactive. The lack of catalysis in complex 12 is rationalized by differences in the steric requirements between the diphenylphosphinites 1-3 (cone angle >140°) and the more sterically hindered cyclohexyl-phosphinite 4 (cone angle >170°) and the resulting stereochemistry on the Pd center. The ligands in complex 12 adopt a... 

Keywords Allylic Alkylation m Asymmetric Catalysis m C2-Symmetry m De-symmetrization m Electronic Differentiation m Heck Reaction m Hydrogenations m Metal Complexes m Modular Design m P,N-Ligands m Steric Differentiation m Respective Control... 

Another significant development in oxazoline chemistry is the application of oxazoline-containing ligands for asymmetric catalysis, such as palladium-catalyzed allylic substimtions, Heck reactions, hydrogenations, dialkylzinc additions to aldehydes, and Michael reactions. The discovery of diastereoselective metalation of chiral ferrocenyloxazolines has further expanded the availability of chiral ligands for metal-catalytic reactions. 

Loiseleur, O., Meier, P. and Pfaltz, A., Chiral phosphanyldihydrooxazoles in asymmetric catalysis enantiose-lective Heck reactions, Angew. Chem., Int. Ed. Engl., 1996, 35, 200-202. 

Arasabenzene, with chromium, 5, 339 Arcyriacyanin A, via Heck couplings, 11, 320 Arduengo-type carbenes with titanium(IV), 4, 366 with vanadium, 5, 10 (Arene(chromium carbonyls analytical applications, 5, 261 benzyl cation stabilization, 5, 245 biomedical applications, 5, 260 chiral, as asymmetric catalysis ligands, 5, 241 chromatographic separation, 5, 239 cine and tele nucleophilic substitutions, 5, 236 kinetic and mechanistic studies, 5, 257 liquid crystalline behaviour, 5, 262 lithiations and electrophile reactions, 5, 236 as main polymer chain unit, 5, 251 mass spectroscopic studies, 5, 256 miscellaneous compounds, 5, 258 NMR studies, 5, 255 palladium coupling, 5, 239 polymer-bound complexes, 5, 250 spectroscopic studies, 5, 256 X-ray data analysis, 5, 257... 

Dendritic catalysis have been used in various chemical reactions, including the Suzuki-Miyaura reaction, Mizoroki-Heck reaction, hydrogenation reaction, carbonylation and hydroformylation reactions, oxidation reaction, polymerization and oligomerization reactions, arylation reaction, alkylation reaction, and asymmetric synthesis [6]. Recently, dendritic catalysts have been reviewed by Astmc et al. [6], In another review article. Reek et al. reviewed the applications of dendrimers as support for recoverable catalysts and reagents [58]. The authors believed that catalytic performance in these systems depends on used dendritic architecture. 

Link, J. T. The Intramolecular Heck Reaction Or tanic Reactions 2002, dO, 157-534. Shibasaki, M. Vogl, E. M. Heck Reaction Comprehensive Asymmetric Catalysis ITII 1999, i, 457-487. 

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