Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• a factor of up to 107 in comparison to Huisgen’s uncatalyzed procedure [13][14]. Since Meldal and Sharpless had first reported this copper-catalyzed variant of Huisgen’s 1,3-dipolar cycloaddition, a myriad of protocols employing different catalyst systems has been described. It is essential for the

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• ]. In the same paper, the authors showed that cobalt perchlorate could also improve the yield of the uncatalyzed reaction. Iron sulfate, on the other hand, gave the same yield as in the absence of added metals. 4 Catalytic trifluoromethylthiolation Aryl trifluoromethyl sulfides (ArSCF3) play an

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

• organocatalyst, dienophile 3 and diene 4 were stirred together at room temperature with an equimolar amount of the prospective organocatalyst in the absence of any solvent. The catalytic performance was classified by the acceleration of the reaction time compared to the uncatalyzed reaction (Table 2, entry 1

• ). 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

• ). To our delight and in contrast to the uncatalyzed reaction conditions (Table 1), just one regioisomer was isolated. In addition, the cycloaddition with thiourea catalyst 10 afforded exclusively the exo-Diels–Alder product 2a, whereby thermal conditions afforded an inseparable mixture of 2a and 2b

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• could be employed for uncatalyzed intermolecular carbometalation. Naturally, many groups envisioned transition-metal-catalyzed carbometalation reactions that directly convert alkynes and alkenes to new organomagnesium and organozinc reagents [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28

• uncatalyzed carbomagnesiation (Scheme 5) [60][61]. This addition proceeded in an anti fashion to give intermediate 2a. The trend is the same in copper-catalyzed reactions of wide scope [62]. In 2001, Negishi applied copper-catalyzed allylmagnesiation to the total synthesis of (Z)-γ-bisabolene (Scheme 6) [63

• aza-Claisen rearrangement. Uncatalyzed carbomagnesiation of cyclopropenes. Iron-catalyzed carbometalation of cyclopropenes. Enantioselective carbozincation of cyclopropenes. Copper-catalyzed facially selective carbomagnesiation. Arylmagnesiation of cyclopropenes. Enantioselective methylmagnesiation of

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

• Fabrice Chemla,
• Florian Dulong,
• Franck Ferreira and
• Alejandro Pérez-Luna

Beilstein J. Org. Chem. 2013, 9, 236–245, doi:10.3762/bjoc.9.28

• uncatalyzed cross-coupling reactions with bromoalkynes, no reaction was observed between Et2Zn and 1-bromohexyne (9) [54]. By contrast, bromoalkyne 11 having a silyloxy group at the propargylic position reacted smoothly to afford ethyl-substituted alkyne 10 along with alkene 12, which had incorporated two

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• solvent. Presumably, the enol tautomer reacts uncatalyzed with F–TEDA, followed by a slow, Lewis acid catalyzed fluorination of the remaining ketone. The catalytic effects of other Lewis acids in the fluorination of 1 were semiquantitatively studied by TLC experiments and found as presented in Scheme 3

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine

• Lisa K. Thalén and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97

• uncatalyzed chemical acylation of the substrate occurs at elevated temperatures when using acyl donors of this type in the DKR of primary amines. This has been overcome by initially adding one equivalent of the acyl donor followed by a later addition of 0.1 equiv of the acyl donor to allow the reaction to go

• be observed. The concentration of the reaction had a large impact on the rate of uncatalyzed acylation. This could be seen in the decrease of enantiomeric excess observed when going from a concentration of 0.2 M to 0.5 M (Table 3, entries 2 and 4). Also, a decrease in the amount of enzyme to