Electron depleted bis(methylene)cyclobutenes: sulfinyl and sulfonyl substitution

Recent advances in the direct transformation of propargylic alcohols to allenes

This review summaries a view of the advances in the direct transformation of propargylic alcohols to functionalized allenes.

Copper-boxmi complexes as highly enantioselective catalysts for electrophilic trifluoromethylthiolations

The enantioselective trifluoromethylthiolation of β-ketoesters using chiral copper-boxmi complexes as catalysts is reported. A number of α-SCF3-substituted β-ketoesters have been obtained with up to >99% enantiomeric excess (ee), and the trifluoromethylthiolated products were then transformed diastereoselectively to α-SCF3-β-hydroxyesters with two adjacent quaternary stereocenters.

The chemistry of bisallenes

This review describes the preparation, structural properties and the use of bisallenes in organic synthesis for the first time. All classes of compounds containing at least two allene moieties are considered, starting from simple conjugated bisallenes and ending with allenes in which the two cumulenic units are connected by complex polycyclic ring systems, heteroatoms and/or heteroatom-containing tethers. Preparatively the bisallenes are especially useful in isomerization and cycloaddition reactions of all kinds leading to the respective target molecules with high atom economy and often in high yield. Bisallenes are hence substrates for generating molecular complexity in a small number of steps (high step economy).

How easy are the syntheses of allenes?

This short review highlights some of the recent important developments on the synthesis of allenes and its applications on the synthesis of some allenic natural products and allenic-based optoelectronic materials.

Fast oxy-cope rearrangements of bis-alkynes: competition with central C-C bond fragmentation and incorporation in tunable cascades diverging from a common bis-allenic intermediate

Fast anionic oxy-Cope rearrangements of 1,5-hexadiyn-3,4-olates can be incorporated into cascade transformations which rapidly assemble densely functionalized cyclobutenes or cyclopentenones via a common bis-allenic intermediate. The competition between fragmentation, 4π-electrocyclic closure, and aldol condensation can be efficiently controlled by the nature of the acetylenic substituents. The rearrangement of bis-alkynes with two hydroxyl substituents opens a conceptually interesting entry in the chemistry of ε-dicarbonyl compounds and suggests a new approach to analogues of rocaglamide/aglafolin.