On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• internal alkyne 6, which was submitted to gold-catalyzed cycloisomerization [33] to afford spiroketals 7a and 7b (the silyl ether is concomitantly hydrolyzed) as a 1:1 mixture of isomers. Exposure of this mixture to zinc chloride promoted isomerization to provide 7a in >20:1 dr. TEMPO oxidation then

• silyl ether 19 with the (R)-propylene oxide produced the internal alkyne 20 (Scheme 5). Gold(I) chloride in MeOH induced the spiroketalization of alkyne 20 with concomitant cleavage of the PMP acetal and partial cleavage of the TBS ether. After completion of the desilylation with TBAF, a mixture of 5,5

Parallel solid-phase synthesis of diaryltriazoles

• Matthias Wrobel,
• Jeffrey Aubé and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

• ) was preswollen in dimethylformamide (2 mL/100 mg resin) for 2 h at room temperature. Subsequently, the catalyst complex pentamethylcyclopentadienylbis(triphenylphosphine)ruthenium(II) chloride, Cp·RuCl(PPh3)2, (5 mol %) and either a terminal or an internal alkyne (4 equiv) were added. After the

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• ), under the optimized cycloaddition conditions (diglyme, microwave irradiation, 120 °C, 20 min), producing the desired α-carbolines in excellent yields (96–98%). However, propargyl amide 13f with the internal alkyne (Table 4, entry 6) required a longer reaction time (40 min) for the cycloaddition to be

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• oxacyclic product 5. Importantly, the reaction also proceeds with non-aromatic 1-oxo-4-alkoxy-5-ynes [40]. Curiously, when the substrate features an internal alkyne, such as in alkynyl acetate 6, the reaction evolves through alternative mechanistic pathways [41]. In particular, Liu showed that in these

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• enyne cycloisomerizations. The new catalytic system has expanded the scope of the reactions to six- and seven-membered ring formations, which had been difficult with the conventional catalytic systems [55]. Furthermore, we found that L1–gold(I) complex efficiently catalyzed the cyclization of internal

• alkyne substrates, which had also been difficult due to the steric repulsion between a nucleophilic center and a terminal substituent on the alkyne moiety [56]. We proposed that the cavity in the ligand forces the nucleophilic center closer to the gold-bound alkyne, resulting in the entropy-based rate

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33