Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• alcohols compared to allyl halides/acetates/carbonates generally necessitates harsher reaction conditions and/or the need for activating agents (i.e., Brønsted or Lewis acids) [3][4]. Recently, late-transition metal (LTM) catalysis (i.e., Hg, Pd, Pt, Au, and Ru) has received growing attention in organic

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• products were obtained in excellent yields (generally >90% yields with 1% loading). Besides the typical ester migrating groups, carbonates and carbamates were also found to be suitable for this transformation, which provided a highly efficient, practical method for the preparation of substituted allenes

• summarized in Table 2. As indicated in Table 2, carbonates (entries 1–5) and carbamate (entry 6) were also suitable for this transformation. Compared to the allene-acetates, the allene-carbonates and allene-carbamates were more stable in water. Notably, although the alkene was considered as a readily

• application of the allene-carbonates and allene-carbamates as building blocks for development of new synthetic methodologies is currently underway in our group. Chemoselective activation of alkyne over allene by the TA–Au catalysts. The counter ligands, an important factor in Au(I) catalysis. The challenge of

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• -methoxyphenylboronic acid or 1 equiv of methanol [52]. Mechanistically, it was proposed that the enones 103 were produced through two pathways (Scheme 19). The gold(I)-catalyzed rearrangement of propargylic tert-butyl carbonates gave diversely substituted 4-alkylidene-1,3-dioxolan-2-ones 115 [53]. For example

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• trapped with internal nucleophiles. For example, Shin and co-workers reported a valuable transformation using the tert-butoxycarbonyl (Boc) group to trap the cation following the activation of π-systems by gold in a route to cyclic carbonates (Scheme 10a) [100]. The Boc-group was considered to be very

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

• performed to reach 24,25-ethanovitamine D3 lactones (Scheme 7) [54]. Recently, conjugated dienes resulting from EYCM of terminal and symmetrical propargylic carbonates with ethylene have been prepared in the presence of Grubbs second generation catalyst II. They have been used in sequential catalytic

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• chlorinated solvents, optimally dichloromethane. Recently however, we showed that catalyst 2 could be used in propylene carbonate [53]. Propylene carbonate and other cyclic carbonates are starting to attract significant interest as green solvents [54][55][56][57][58][59][60][61][62][63][64], since they can be

• . Synthesis of cyclic carbonates. Synthesis of cyanohydrin trimethylsilyl ethers and acetates. Equilibrium between bimetallic and monometallic Ti(salen) complexes. Influence of solvent on cyanohydrin synthesis using catalysts 1 and 2. Optimization of asymmetric cyanohydrin synthesis catalysed by complex 2 in

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• cinnamylation of electron-rich arenes. Employing, for instance, p-xylene or toluene and cinnamyl alcohols or -carbonates 54 in the presence of 10 mol% of Mo(CO)6 the desired allylated arenes 55 could be isolated in good yields (Scheme 24A) [72]. As application of this methodology, methyleugenol 57, an

• of Mo(CO)6 as a catalyst required exclusion of air and moisture. Moreover, the reactive allyl carbonates or acetates had to be applied due to the easier activation as better leaving groups. Hence, improved procedures with less sensitive and cheaper catalysts as well as unprotected alcohols had to be

Synthesis of 3-(phenylazo)-1,2,4-triazoles by a nucleophilic reaction of primary amines with 5-chloro- 2,3-diphenyltetrazolium salt via mesoionic 2,3-diphenyltetrazolium- 5-aminides

• Shuki Araki,
• Satoshi Hirose,
• Yoshikazu Konishi,
• Masatoshi Nogura and
• Tsunehisa Hirashita

Beilstein J. Org. Chem. 2009, 5, No. 8, doi:10.3762/bjoc.5.8

• and tert-butylamine) are considered to be difficult to give the cyclized intermediate C. The less efficient behaviour of the carbonates in the deprotonation process may be attributed to the heterogeneous reaction system. In the last oxidation stage from C to 3, aminotetrazolium 4 is considered also to

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

• . Results and Discussion On installation of pyrimidine bases into the gem-difluorinated allylic carbonates 1 and 4, our group found that the γ-substitution products 2, 3 and 5 were surprisingly generated exclusively in good yields, respectively, when the compounds 1 and 4 reacted with suitably protected

Study of thioglycosylation in ionic liquids

• Jianguo Zhang and
• Arthur Ragauskas

Beilstein J. Org. Chem. 2006, 2, No. 12, doi:10.1186/1860-5397-2-12

• species, as shown in Figure 1. A broader spectrum of anionic counter ions have been reported, including: halides, carbonates, sulfonates, tetrafluorborates, nitrates and chloroaluminates. Changes in the physical properties of ionic liquids, including their melting point, hydrophilicity, lipophilicity and

Do α-acyloxy and α-alkoxycarbonyloxy radicals fragment to form acyl and alkoxycarbonyl radicals?

• Dennis P. Curran and
• Tiffany R. Turner

Beilstein J. Org. Chem. 2006, 2, No. 10, doi:10.1186/1860-5397-2-10

• reaction because the precursors are readily available and stable (α-halo acetates and carbonates are not stable) and because the intermediate radicals resemble Wille's typical intermediates. The syntheses of precursors 11a and 11b are summarized in Scheme 1. Copper-mediated conjugate addition of 3