Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• -acylpyrroles [265] (Scheme 39). In their work, diethylzinc and 147 acts as a bifunctional catalyst system where the α,β-unsaturated system is activated through Lewis acid coordination and the catalyst acts as a directing group for the phosphite. Overall the reaction proceeds in both high yield and

Comparing kinetic profiles between bifunctional and binary type of Zn(salen)-based catalysts for organic carbonate formation

• Carmen Martín and
• Arjan W. Kleij

Beilstein J. Org. Chem. 2014, 10, 1817–1825, doi:10.3762/bjoc.10.191

• was done between the binary catalyst system Zn(salphen)/NBu4I and a bifunctional system Zn(salpyr)·MeI with a built-in nucleophile. The latter system demonstrates an apparent second-order dependence on the bifunctional catalyst concentration and thus follows a different, bimetallic mechanism as

• minimal reaction temperature required for the bifunctional catalyst to provide a sufficiently disaggregated state and thus the required Lewis acid centers for catalytic turnover when combined with NBu4I (Figure 9). At this temperature individual catalytic conversions for bifunctional complex 2 and

• first-order dependence on catalyst concentration for the binary system was found in line with previous computational work on this system [36] while a second-order rate dependence was observed for the bifunctional catalyst 2. These observations thus support a monometallic mechanism when Zn species 1 and

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• for Au NP, and these heterogeneous systems were tested as recyclable catalysts in an A3-coupling. The former was effective in three simple model reactions as a bifunctional catalyst (Au/acid) in aqueous medium at 70 °C. The latter works well in chloroform at 60 °C and tolerates a number of substituted

Organocatalytic asymmetric selenofunctionalization of tryptamine for the synthesis of hexahydropyrrolo[2,3-b]indole derivatives

• Qiang Wei,
• Ya-Yi Wang,
• Yu-Liu Du and
• Liu-Zhu Gong

Beilstein J. Org. Chem. 2013, 9, 1559–1564, doi:10.3762/bjoc.9.177

• basis of experimental observations, we proposed a reaction mechanism (Scheme 1). The phosphoric acid acts as a bifunctional catalyst and simultaneously activates both the tryptamine derivative and N-PSP by hydrogen-bonding interaction. Then, the asymmetric selenofunctionalization occurred at the 3

Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• ). At first, the use of MacMillan's imidazolidinone organocatalyst 6 [12] was examined, but no catalytic effect was observed (Table 2, entry 2). The usage of L-proline as a bifunctional catalyst only gave a slight improvement compared to the uncatalyzed reaction (Table 2, entry 3). Whereas the addition

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• employing a chiral pyrrolidine bearing a 2-mercaptopyridine moiety as organocatalyst (VII) and simple α-amino acids, such as tert-leucine, as co-catalyst. The asymmetric transformation proceeds by simultaneous activation of cyclic enones 13 and aldehyde 1 by the bifunctional catalyst VII and the amino acid

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• , the increase in temperature resulted in a small drop in stereoselectivity for the model reaction with catalyst VII. The mechanism of the reaction is believed to be similar to that previously reported for 1,3-dicarbonyl compounds and acyl phosphonates [23]. Squaramide IX is a bifunctional catalyst that

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• [26][27]. To construct the C3 quaternary stereogenic carbon center, we have designed a novel cinchona alkaloid-based phosphoramide bifunctional catalyst to realize a highly enantioselective Michael addition of both unprotected 3-alkyl- and 3-aryloxindoles to nitroolefins [28]. Based on these results

Asymmetric organocatalytic decarboxylative Mannich reaction using β-keto acids: A new protocol for the synthesis of chiral β-amino ketones

• Chunhui Jiang,
• Fangrui Zhong and
• Yixin Lu

Beilstein J. Org. Chem. 2012, 8, 1279–1283, doi:10.3762/bjoc.8.144

• employing β-keto acids as the donor. The reaction was effectively catalyzed by cinchonine-based bifunctional catalyst C-1, and the synthetically useful β-amino ketones were prepared in excellent yields and with moderate to good enantioselectivities. The method reported represents a new protocol for the

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• -component coupling reaction (Scheme 8). As described in our previous communication [61], the employment of bifunctional catalyst 9 [54][55] in a highly stereoselective two-stage one-pot cascade led to the formation of enantiomerically highly enriched spirocycle (+)-1a (Scheme 8). In a repeat of the process