Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• PAH substituents (Scheme 3). Pd-catalyzed coupling of the diiodo compound 14 with the mono protected bisacetylene 20, deprotection of the acetylenes with TBAF and subsequent coupling with an excess of the diiodo compound 5c gave the diiodide 23. Hagihara-Sonogashira coupling of 23 with an excess of

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• acetylenes prepared and used in silyl ether-tethered Pauson-Khand reactions. Yields correspond to yield of the silyl ether formed, figures in brackets from the Pauson-Khand reaction. Chain-functionalised acetylenes prepared and used in silyl ether-tethered Pauson-Khand reactions. Yields correspond to yield

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• -1-ones 15–16 (Scheme 3), which are not easily prepared by classical methods, and for which few methods of synthesis have been reported in the literature. [7][13] Silylcupration of acetylenes is also a powerful tool for cyclopentane annulations. Terminal alkynes 17–19 bearing electron-withdrawing

• the corresponding mesylate and fluoride-induced intramolecular displacement led to methylenecyclobutanes 41 in good yields (Scheme 8). [22] A different approach, starting from acetylenes instead of allenes and using silyl- or stannylcuprates followed by addition of an epoxide as electrophile, led to

• oxacycloalkenes has been achieved by intramolecular cyclization of functionalised allylsilanes obtained from optically active allylic alcohols (Scheme 12). [26] Conclusion In summary, the metallocupration (Si-Cu and Sn-Cu) of allenes and acetylenes has proven to be extremely useful for the construction of cyclic