Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• developments in nucleophilic chiral phosphine-catalyzed asymmetric reactions, including annulations of allenes, ketenes, alkynes, and Morita–Baylis–Hillman (MBH) carbonates with activated alkenes and imines, allylic substitution of MBH acetates and carbonates, Michael additions, γ-umpolung additions, and

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• ][38][39][40] or Pd0-allylic substitution [42][43] of alkenols having an allylic OR group and additional halocyclisation. Conclusion In summary, we have developed the syntheses of several unsaturated alcohols. The chiral alkenols 20–28, 34–37 and 43 represent useful C5–C12 chain building blocks. The

Synthesis of 1-[bis(trifluoromethyl)phosphine]-1’-oxazolinylferrocene ligands and their application in regio- and enantioselective Pd-catalyzed allylic alkylation of monosubstituted allyl substrates

• Zeng-Wei Lai,
• Rong-Fei Yang,
• Ke-Yin Ye,
• Hongbin Sun and
• Shu-Li You

Beilstein J. Org. Chem. 2014, 10, 1261–1266, doi:10.3762/bjoc.10.126

• range of substrates. Keywords: allylic substitution; enantioselectivity; ferrocene; organophosphorus; palladium; regioselectivity; Introduction The palladium-catalyzed asymmetric allylic alkylation (AAA) reaction is now becoming an efficient method for the construction of carbon–carbon bonds [1][2][3

• ][4][5]. Despite extensive investigation and noteworthy advances in this field, several challenges remain to be solved. For instance, with monosubstituted allyl substrates, the palladium-catalyzed allylic substitution reaction prefers to give linear products rather than the branched ones [6][7][8][9

• ] (Scheme 1). Accordingly, the regio- and enantioselective allylic substitution reaction of monosubstituted allylic substrates to preferably obtain the branched products is one of the continuing challenges. To our knowledge, there are several cases in which high levels of both regio- and enantioselectivity

Enantioselective synthesis of planar chiral ferrocenes via palladium-catalyzed annulation with diarylethynes

• Yan-Chao Shi,
• Rong-Fei Yang,
• De-Wei Gao and
• Shu-Li You

Beilstein J. Org. Chem. 2013, 9, 1891–1896, doi:10.3762/bjoc.9.222

• ). The allylic substitution reactions of (rac)-4 had been carried out. The allylic alkylation reaction proceeded in 95% yield and 44% ee (Scheme 3, reaction 1) and the allylic amination reaction proceeded in 32% yield and 43% ee (Scheme 3, reaction 2) [69][70][71]. Although only moderate

• could be transformed readily into a P,N-ligand, which was found to be suitable for Pd-catalyzed allylic substitution reactions. Experimental General procedure for the enantioselective synthesis of planar chiral ferrocenes To a solution of alkyne 2 (0.46 mmol) in DMA (1.5 mL) was added Boc-L-Val-OH (8.7

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• was shown that chiral multifunctional thiourea-phosphines were excellent catalysts for the asymmetric aza-MBH reaction, asymmetric allylic substitution of MBH adducts, and asymmetric [3 + 2] annulation of MBH carbonates with electron-deficient olefins [52][53][54][55][56]. Hence, we initially used

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• and enones, as well as in palladium-catalyzed allylic substitution reactions [14][15][16][17][18][19][20]. Thus, the synthesis of specifically functionalized pyridines is of considerable interest, and many approaches toward this heterocyclic structure have been disclosed in the literature [21]. In

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• -withdrawing groups will enhance the stability of the complex [25][26]. The next step is the ionization step followed by allylic substitution. The final step is the decomplexation. Trost et al. [3] and Fiaud et al. [6] have proposed that only metal–olefin complexation anti to the leaving group will lead to the

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• transformations in the presence of ruthenium catalysts, which are able to perform regioselective allylic substitution by O-, N- and C-nucleophiles (Scheme 8a) [55] and elimination to provide a new access to dendralenes (Scheme 8b) [56]. Higher olefin–alkyne cross-metathesis This cross-metathesis reaction was

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• , Shanghai 201620, China 10.3762/bjoc.4.18 Abstract We present a mechanistic investigation of Pd-catalyzed allylic substitution of cyclic gem-difluorinated carbonates 1 and 4, previously employed in the synthesis of 3',3'-difluoro-2'-hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides in 17 steps. The

• allylic substitution, in which the regioselectivity was reversed from that of nonfluorinated substrates. This reversed regioselectivity caused by fluorine interests us greatly. Herein, we present a mechanistic investigation of Pd-catalyzed allylic substitution of cyclic gem-difluorinated carbonates

• our knowledge, the effect of gem-difluoromethylene group on Pd-catalyzed cyclic allylic substitution has never been addressed so far. The regioselectivity was totally different from those of nonfluorinated substrates [18]. Unexpected and specific regioselectivity of Pd-catalytic asymmetric reactions

A superior P-H phosphonite: Asymmetric allylic substitutions with fenchol- based palladium catalysts

• Bernd Goldfuss,
• Thomas Löschmann,
• Tina Kop-Weiershausen,
• Jörg Neudörfl and
• Frank Rominger

Beilstein J. Org. Chem. 2006, 2, No. 7, doi:10.1186/1860-5397-2-7

• -ligands (Table 1). Conclusion Besides P, N-bidentate FENOP ligands, monodentate BIFOP ligands can be employed successfully in Pd-catalyzed allylic substitution of 1-phenyl-2-propenyl acetate with dimethylmalonate. Surprisingly, the halogen phosphites BIFOP-Cl and BIFOP-Br are stable towards nucleophiles

• extrapolated energies: BIFOP-H-re: -1025.01553 H, BIFOP-H-si: -1025.01466 H. The by 0.5 kcal mol-1 slightly preferred re-addition of the NH3 model nucleophile corresponds to the experimental S-alkylation product. Pd-catalyzed allylic substitution with unsymmetrical substrates (Nu = dimethylmalonate, Nf = OAc