Heck coupling asymmetric

Choudary, B.M., Chowdari, N.S., Mahdi, S., Kantam, M.L. (2003) A Trifimctional Catalyst for One-Pot Synthesis of Chiral Diols via Heck Coupling-N-Oxidation-Asymmetric Dihydroxyla-tion Application for the Synthesis of Diltiazem and Taxol Side Chain. Journal of Organic Chemistry, 6S, 1736-1746. 

Scheme 3 Asymmetric Heck coupling of 3,4-dihydrofuran and iodobenzene in the presence of Pd complexes 9-12 giving a mixture of regio and stereo isomers a) 2(R)-phenyl-2,3-dihydrofuran, b) 2(R)-phenyl-2,5-dihydrofuran c) 2(S)-phenyl-2,3-dihydrofuran d) 2(S)-phenyl-2,5-dihydrofuran.

The synthesis of lycorane (13) by Mori and Shiba-saki121 is breathtaking for its use of three consecutive Pd catalyzed C-C bond forming reactions. Thus, Pd-catalyzed asymmetric allylic substitution of a benzoate in meso 7 in the presence of the chiral bisphos-phine 8 leads to the regioselective formation of 10 in 40 % ee It is easy to overlook this low level of enantioselectivity when we are faced with the subsequent elegant Pd-catalyzed reactions Pd-catalyzed intramolecular animation is followed by a Pd-catalyzed Heck coupling to afford 12, which is then readily converted to the target molecule... 

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... 

The phosphine-thiazole ligand 149 has been shown to promote asymmetric intermolecular Heck coupling of 2,3-dihydrofuran with aryl triflates <07ASC2595>. Microwave irradiation of a mixture of 2,3-dihydrofuran (6 equiv.), aryl triflates (1 equiv.) and DIPEA (3 equiv.) in THF in the presence of Pd2(dba)3 (3 mol%) and the ligand 149 (6 mol%) at 120 °C provides 2-aryl-2,5-dihydrofurans 150 in high enantioselectivity. Other phosphine-thiazole ligands have also been evaluated, and ligand 149 proves to be the best in terms of enantioselectivity. 

Scheme 3-49 Ligand-induced asymmetric Heck coupling of 2,3-dihydrofuran [205-207],...

Alternatively, tetrahydroanthracene 85 was also obtained directly from symmetrical ditriflate 86 by a Suzuki cross-coupling/asymmetric Mizoroki-Heck cascade reaction. In this case, reaction of ditriflate 86 with alkylborane 82, Pd(OAc)2, (S)-BINAP and K2CO3 in THF at 60 °C directly gave product 85 in high enantiopurity, albeit in 20% yield. Although the yield for this one-pot conversion was poor, this transformation represents a novel application of the asymmetric Mizoroki-Heck cyclization and remains the only reported example of cascade Suzuki cross-coupling/asymmetric Mizoroki-Heck cyclization. A series of additional synthetic transformations was required to convert 85 to pentacyclic intermediate 87, which had earlier been converted by Harada et al. [53] to halenaquinone (88) and halenaquinol (89). 

As mentioned above, the enantioselective desymmetrization of prochiral, as well as meso compounds, by using a Mizoroki-Heck coupling represents another pos-sibiUty to effect asymmetric transformations [81-84]. Therefore, the plane of symmetry in these precursors must be broken by differentiation of enantiotopic alkene-containing groups with a chiral palladium complex. 

Scheme 8.59 A one-pot sequence of the Heck coupling with subsequent asymmetric cis dihydroxylation [385]. LDH-PdOsW is a mixture of PdClj, OSO4 and WO4 on a layered double hydroxide (LDH)-modified silica.

The treatment of the dienediol bisnonaflate 309 containing an ( >— 1)-alkenyl substituent with the typical Heck precatalyst cocktail in the presence of an external alkene, such as an acrylate, gives rise to the formation of the bicyclic tetraene 310 by an intramolecular Heck coupling followed by an intermolecular Heck coupHng (Scheme 8.66) [239]. This reaction can be performed using chiral catalysts to achieve asymmetric induction with up to 30% ee (cf. Scheme 8.77). 

Homillos V, van Zijl AW, Feringa BL (2012) Catalytic asymmetric synthesis of chromenes and tetrahydroquinolines via sequential allylic alkylation and intramolecular Heck coupling. Chem Commun 48 3712-3714... 

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