Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• -catalyzed [2 + 2 + 3] cycloaddition reaction of these compounds with nitrones giving rise to functionalized 1,2-oxazepane derivatives XIII. This cascade process takes place through the interception of the 1,4-dipole equivalent XII generated by an initial 5-exo cyclization, although with some gold catalysts

Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

• Koichiro Miyazaki,
• Yu Yamane,
• Ryuichiro Yo,
• Hidemitsu Uno and
• Akio Kamimura

Beilstein J. Org. Chem. 2013, 9, 1326–1332, doi:10.3762/bjoc.9.149

• treatment of chiral enyne compounds. A good trans-selectivity was observed in the reaction. Results and Discussion We examined the cascade process using optically active enyne precursor 1a, which was prepared by a Michael/aldol domino reaction to chiral sulfinimines followed by thermal elimination and N

Anionic cascade reactions. One-pot assembly of (Z)-chloro-exo-methylenetetrahydrofurans from β-hydroxyketones

• István E. Markó and
• Florian T. Schevenels

Beilstein J. Org. Chem. 2013, 9, 1319–1325, doi:10.3762/bjoc.9.148

• -methyleneketals [1][2][3]. This unique transformation is particularly efficient in the case of six-membered ring ketones (Scheme 1). In an attempt to extend the scope of this cascade process to acyclic ketones, acetone was submitted to the usual reaction conditions. To our surprise, the expected adduct 5 was

• that good to excellent yields of (Z)-chloro-exo-methylenetetrahydrofurans could be obtained by the judicious choice of the bases employed to promote this cascade process. Having delineated some suitable conditions, the scope and limitations of this methodology were investigated [17][18][19][20][21][22

• 59, or it may undergo addition of a water molecule, affording the hemiketal 60. Addition of a proton to the vinyl ether function, followed by intramolecular capture by the hydroxy group, finally provides the unique bridged adduct 62. Conclusion In summary, a unique anionic cascade process, leading to

Cascade radical reaction of substrates with a carbon–carbon triple bond as a radical acceptor

• Hideto Miyabe,
• Ryuta Asada and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2013, 9, 1148–1155, doi:10.3762/bjoc.9.128

• chiral Lewis acid and these substrates. Keywords: cascade; cyclization; enantioselective; free radical; Lewis acid; radical; Introduction Strategies involving a cascade process offer the advantage of multiple carbon–carbon and/or carbon–heteroatom bond formations in a single operation. Radical

• cascade process, the reactions of propiolic acid derivatives 7 and 8 were tested (Scheme 4). At first, the reaction of 7 was evaluated under asymmetric reaction conditions. However, the cascade addition–cyclization–trapping reaction did not proceed, and the simple adduct 10 was formed in 57% yield by the

Aqueous reductive amination using a dendritic metal catalyst in a dialysis bag

• Jorgen S. Willemsen,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 960–965, doi:10.3762/bjoc.9.110

• examples, we decided to design a metallodendrimer that would show catalytic activity in a cascade process while compartmentalized under aqueous conditions. To this end, an iridium catalyst was selected that was known to be suitable for reductive amination in an aqueous environment. We showed that by

Synthesis of skeletally diverse alkaloid-like molecules: exploitation of metathesis substrates assembled from triplets of building blocks

• Sushil K. Maurya,
• Mark Dow,
• Stuart Warriner and
• Adam Nelson

Beilstein J. Org. Chem. 2013, 9, 775–785, doi:10.3762/bjoc.9.88

• competed with the expected metathesis cascade process. Finally, it was demonstrated that the metathesis products could be derivatised to yield the final products. At each stage, purification was facilitated by the presence of a fluorous-tagged protecting group. Keywords: alkaloids; cyclopropanes

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• synthesis of phosphorothioate oligonucleotides [57], was synthesized by the reaction of 2-mercaptobenzoic acid (7) with KSCOMe (1), probably through the intermediate 8 (Scheme 3) [58]. We envisioned that compound 6 could be easily achieved by a cascade process starting with the copper-mediated reaction of 2

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• , pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• (Scheme 32) [79]. Indeed, the reaction carried out with 10 mol % of PdCl2(MeCN)2 as catalyst and a stoichiometric amount of 1,4-benzoquinone in DMF/THF as solvent underwent an oxidative cascade process involving the sequential intramolecular formation of C–N and C–C bonds, with an oxidative coupling

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

• -unsaturated nitro compounds 27 in toluene afforded chiral thiochromans 51 bearing three continuous stereogenic centers with high diastereo- and enantioselectivities by this novel cascade process (Scheme 26). 3. Organocatalytic aza-Michael reactions to access functionalized 1,2-dihydroquinolines 3.1. Reaction

Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine

• Jessica Baiget,
• Sabin Llona-Minguez,
• Stuart Lang,
• Simon P. MacKay,
• Colin J. Suckling and
• Oliver B. Sutcliffe

Beilstein J. Org. Chem. 2011, 7, 1407–1411, doi:10.3762/bjoc.7.164

• shows that although Lewis acids can be used to activate Pictet–Spengler reactions, the absence of a Lewis acid is optimum for this one-pot cascade process. β-Carboline 6 is a useful intermediate, used by Panosyan and Still [22] in their synthesis of xestomanzamine A. We wished to apply the preparation

• , functionalised β-carboline 6 has been synthesised by a manganese dioxide mediated one-pot oxidation, condensation, Pictet–Spengler cyclization, dehydrogenative-aromatisation cascade process. This procedure was then applied as the key step in our divergent synthetic strategy for formation of the naturally

• dioxide has a dual purpose in the reaction. Firstly, it is used for the oxidation of the starting alcohol 1 and secondly it is used in order to promote the aromatisation [20] of tetrahydrocarboline 5, allowing effectively at least three operational steps to be carried out as part of a single cascade

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• still-operative palladium complex. To do so, a terminal alkyne and caesium carbonate were added to the reaction mixture containing the newly formed 4-iodopyrrole, and the reaction temperature was increased to 70 °C (Scheme 17) [17]. Grigg and coworkers reported a three-component cascade process for the

Efficient gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation of unactivated alkenes with α-ketones

• Ya-Ping Xiao,
• Xin-Yuan Liu and
• Chi-Ming Che

Beilstein J. Org. Chem. 2011, 7, 1100–1107, doi:10.3762/bjoc.7.126

• simple starting materials [41]. We initially envisioned that the gold(I)-catalyzed cascade process could be established starting from the intermolecular N-Michael reaction of α,β-unsaturated ketone 1 and substituted allylamine 2 to furnish an α-ketone intermediate I [42][43][44] (for gold-catalyzed

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

• . Many strategies have been developed to make the Au(I)-activated allene esters react with other proper substrates, forming interesting new products in a cascade fashion. The indene synthesis (Scheme 2b), reported by Nolan and coworkers, is one good example highlighting the importance of the cascade

• process [35]. As shown in Scheme 2b, with the [IPr–Au]+ catalyst, only trace amount of the allene 2a was obtained. The major product derived from the Friedel–Crafts addition of the aromatic ring to the gold activated allene. Therefore, selective activation of the alkyne over the allene was considered as a

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• -catalysed cascade process provided an efficient entry to substituted indoles [25]. Although copper is less toxic and less expensive than palladium, the required harsh conditions, the limited range of suitable substrates and moderate yields prevented the use of Ullmann-type reaction from reaching its full

• bromide affected the yield only marginally [63]. A second example of intramolecular coupling is the synthesis of promazine drugs (56) that are interesting due to their clinical use for psychotropic medication. The CuI/L-proline-catalysed cascade process, developed by Ma et al., gave the best yields when 2