Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

• Marie Hoffmann,
• Solène Miaskiewicz,
• Jean-Marc Weibel,
• Patrick Pale and
• Aurélien Blanc

Beilstein J. Org. Chem. 2013, 9, 1774–1780, doi:10.3762/bjoc.9.206

• catalysts with their carbophilic character have emerged as a new tool for furan preparation. As summarized in Scheme 1, furans could now be obtained by either gold(I) or gold(III) catalysis from various types of substrates such as allenyl ketones [8][9][10][11][12][13][14], enynes or diynes [15][16][17

Microwave-assisted three-component domino reaction: Synthesis of indolodiazepinotriazoles

• Rajesh K. Arigela,
• Sudhir K. Sharma,
• Brijesh Kumar and
• Bijoy Kundu

Beilstein J. Org. Chem. 2013, 9, 401–405, doi:10.3762/bjoc.9.41

• increasing attention in drug discovery processes [17][18]. The ease of reaction in the intermolecular format has been successfully demonstrated by using both organic/inorganic azides as well as alkynes/diynes [19][20][21]. In contrast to its employment in an intermolecular format, intramolecular azide–alkyne

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

• group; (2) alkynes bearing a directing group; (3) strained cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon–carbon unsaturated bonds (allenes, dienes, enynes, or diynes). Keywords: alkene; alkyne; carbomagnesiation; carbometalation; carbozincation; transition

• bearing a directing group; (3) cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon–carbon unsaturated bonds (allenes, dienes, enynes, or diynes). Review Carbomagnesiation and carbozincation of electron-deficient alkynes Since conjugate addition reactions of

• -phenyl-1-octyne with 4c provided the corresponding alkylated products 4d exclusively without contamination by the hydromagnesiated products of alkynes. In contrast, Nakamura reported the iron-catalyzed hydromagnesiation of diarylacetylenes and diynes with ethylmagnesium bromide as a hydride donor without

Highly stereocontrolled synthesis of trans-enediynes via carbocupration of fluoroalkylated diynes

• Tsutomu Konno,
• Misato Kishi and
• Takashi Ishihara

Beilstein J. Org. Chem. 2012, 8, 2207–2213, doi:10.3762/bjoc.8.249

• ; carbometallation; diyne; enediyne; fluorine; highly regioselective; highly stereoselective; Introduction trans-Enediynes (trans-hex-3-ene-1,5-diynes), as shown in Figure 1, are well-recognized as one of the most important building blocks because they are frequently utilized for the synthesis of π-conjugated

• . Finally, the thus-obtained iodide underwent a smooth Sonogashira cross-coupling reaction to afford the various desired trans-enediyne derivatives in high yields. trans-Enediyne. Regio- and stereoisomers. Synthetic strategy for the preparation of trifluoromethylated diynes. Preparation of various enynes. A

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• possible by making use of other metal complexes such as Pd [21][22] and Co [23][24][25], but recent advances in iridium chemistry have expanded the scope of the metal complexes that can be used. Common Ir-catalyzed cycloadditions include [2 + 2 + 2] cycloadditions of diynes [11][12][13] or enynes [16] with

• ], diynes [40][41], and triynes [42][43][44]. Conversely, formation of intermediate 5 is rare, likely due to competition with oxidative insertion of the metal into the carbon–halide bond; however, there are reported cases of Co-catalyzed [2 + 2 + 1] [45], Ru-catalyzed [2 + 2] [46], and Rh-catalyzed [4 + 2

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

• -catalyzed endo-cyclizations of 1,4-diynes 20 to seven-membered ring heterocycles 21 [27]. The cyclization occurs exclusively in an endo-fashion under mild conditions and provides access to dihydrodioxepines and tetrahydrooxazepines. The dioxabicyclo[4.2.1] ketal 23 and its further transformation product

• + 2] cycloaddition product in very good yield (Scheme 41). Enynes [110][111][112][113][114][115][116], diynes [117][118][119][120], allenynes [121][122][123][124][125][126][127][128], and dienes [129][130][131] are common substrates for intramolecular cycloaddition reactions. Porcel et al. found that

• benzannulation of 3-alkoxy-1,5-enynes 236 to produce functionalized benzenes 237 [112]. The reaction occurs selectively through a 6-endo-dig pathway to give tri- and tetrasubstituted benzenes efficiently. Cyclization reactions of 1,6-diynes (2,2-dipropargylmalonates 238) could be achieved with gold(I) catalysts

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• chemistry. This mini-review focuses on the most recent achievements on gold-catalyzed oxygen transfer reactions of tethered alkynones, diynes or alkynyl epoxides to cyclic enones. The corresponding mechanisms for the transformations are also discussed. Keywords: alkyne–carbonyl metathesis; cyclic enones

• isolated as the major product. The latter was considered to be an intermediate in the reaction and moreover, the isolated compound 15 could be transformed into the final product 14 under the mediation of p-toluenesulfonic acid. Gold-catalyzed formation of cyclic enones from diynes Zhang and co-workers

• reported gold-catalyzed cyclizations to cyclohexenones 17, employing terminal 1,6-diynes 16 as substrates in the presence of a Brønsted acid and 1 equiv of water (Scheme 12) [48]. None of the desired products were obtained in the absence of the gold catalyst, the Brønsted acid or water. Interestingly, when

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

• diynes protected by a silyl group are also reactive with high regioselectivity [64]. Cross-metathesis of p-substituted styrenes with a propargylic benzoate catalyzed by catalyst II in refluxing benzene has been performed in almost quantitative yields with perfect regioselectivity leading to 1,3

Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

• Reinhold Zimmer,
• Elmar Schmidt,
• Michal Andrä,
• Marcel-Antoine Duhs,
• Igor Linder and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

• treatment of 9c with boron trifluoride etherate in the presence of an excess of 1-hexyne via an azapyrylium intermediate [34][35]. Additional investigations are required to optimize the preparation diynes of type 11. Conversion of the new functionalized 6H-1,2-oxazines to highly substituted pyridine