Synthesis of indole-based propellane derivatives via Weiss–Cook condensation, Fischer indole cyclization, and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Arti Tiwari

Beilstein J. Org. Chem. 2013, 9, 2709–2714, doi:10.3762/bjoc.9.307

• potential drugs for the treatment of schizophrenia and alcohol addiction [34]. However, the synthesis of indole alkaloid derivatives containing a propellane ring system is a challenging task due to the presence of quaternary centers involved with these systems [35]. We envisioned a new synthetic route to

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

• carbenes, guanidines, thioureas, amidinium ions, diols, and Brønsted acids showed their value to give densely functionalized Diels–Alder products in high selectivities [1][2][3][4][5][6][7]. In addition, some organocatalysts enabled even the formation of quaternary centers in Diels–Alder cycloadditions [3

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• the cycloadditions efficiently incorporated consecutive quaternary centers into the complex fused skeleton, overriding the considerable steric hindrance of the dipolarophiles composed of the tri- and even tetra-substituted olefin groups. To test the generality of the site-selective cycloaddition at

Gold(I)-catalyzed formation of furans by a Claisen-type rearrangement of ynenyl allyl ethers

• Florin M. Istrate and
• Fabien Gagosz

Beilstein J. Org. Chem. 2011, 7, 878–885, doi:10.3762/bjoc.7.100

• involves a Claisen-type rearrangement that allows the efficient creation of quaternary centers under mild experimental conditions. Keywords: Claisen rearrangement; furans; gold-catalysis; quaternary centers; Findings Furans represent an important class of heteroaromatic compounds, which are found in a

• ether substrates are easily accessible via various methods (see Supporting Information File 1 for more details), • the Claisen-type rearrangement would allow the formation of two new C–O and C–C bonds in a single step, • the reaction would allow the easy formation of quaternary centers and the

• employed and the easy formation of quaternary centers. The selectivity observed in the structure of the final product is in agreement with the postulated Claisen-type rearrangement. Further studies related to the development of an asymmetric version of this new gold(I)-catalyzed process and its application