Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• heterocyclic compounds have been efficiently generated by means of organocatalytic domino reactions [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69]. In 2009 and 2010, List et al. and the Brière group both reported, separately, the enantioselective synthesis of 2

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

• -benzothiopyrans 37 using the closely related catalyst Ia through the same iminium-enamine activation mode of the α,β-unsaturated aldehydes 2. The asymmetric domino reactions proceeded with high yields (53–93%) and with excellent chemo- and stereoselectivities (up to 98% ee) in chloroform as solvent (Scheme 19

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• , Germany Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland 10.3762/bjoc.8.160 Abstract After prosperous domino reactions towards benzopyrans, the products were used as the starting material in Lewis acid catalyzed and

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• further manipulations on the alkynyl residue. Our previous studies also revealed that even carbohydrate-derived alkynes can be utilized under these reaction conditions in an efficient manner [23]. Our recent interest in domino reactions starting with 2-brominated glycals [26][27][28] motivated us to

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

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• domino reactions. Review Gold-catalyzed alcohol substitution Scope and limitations In the past few years, homogeneous gold catalysis has emerged as an efficient tool to activate triple bonds for the addition of various nucleophiles to alkynes. We initially anticipated that, through coordination to π-bond

• might be expected under gold catalysis conditions. For example, it could be interesting to combine both Lewis and π-acidities to promote domino reactions [44][45]. Domino reactions in the presence of bi-nucleophiles We anticipated that by using bi-nucleophiles HNu1–Nu2H, the first nucleophilic

• impressive enantioselective intramolecular direct allylic substitutions using chiral gold(I) complexes [87][88]. We also took advantage of the π- and σ-(Lewis) acidities of gold(III) complexes to promote domino reactions with bi-nucleophiles such as protected hydroxylamines. In the presence of gold(III), the

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

• scaffolds. Likewise, processes are discussed where mostly identical starting materials are transformed into diverse frameworks depending on whether gold or iodonium activation was used to trigger the reaction. Keywords: catalysis; cycloisomerizations; domino reactions; gold; iodine; Introduction Over the

• past decade, the diverse reactivity of carbophilic Lewis acids has attracted considerable interest in the development of domino reactions [1][2][3][4][5] that are initiated by the catalytic activation of π-systems [6][7][8][9][10][11][12][13]. In particular, the utilization of gold pre-catalysts has

• transformations There are several gold-catalyzed processes for which there are no corresponding iodine counterparts. In general, most of the processes specific for gold are assumed to proceed via gold carbene intermediates. For example, 1,5-enynes 49 can react in gold-catalyzed domino reactions that include a 1,2