Facile Access to Cyclooctanoid Ring Systems via Microwave-Assisted Tandem 6-exo dig Cyclization-Rearrangement Sequence

Hydrogen Bonding-directed Sequential 1,6/1,4-Addition of Heteroatom Nucleophiles onto Electron-deficient 1,3-Diynes

The hydrogen bonding-directed sequential 1,6/1,4-additions developed herein allow for creating unique heterocycles with structural diversity under mild conditions without using metal catalysts or organometallic reagents.

Utilization of the Thorpe-Ingold Effect in the Synthesis of Cyclooctanoid Ring Systems via Anionic 6-exo-dig Cyclization/Claisen Rearrangement Sequence

We demonstrate a facile approach for the synthesis of gem-disubstituted cyclooctanoids, a motif found in several biologically active compounds. Appropriately substituted 1-alkenyl-5-pentyn-1-ols bearing gem-dialkyl substituents at either the C2, C3, or C4 position serve as useful precursors to a number of cyclooct-4-enone derivatives via a tandem, microwave-assisted oxyanionic 6-exo-dig cyclization/Claisen rearrangement reaction. gem-Dialkyl activation is necessary for these reactions to occur, as unactivated 1-alkenyl-5-pentyn-1-ols fail to undergo 6-exo-dig cyclization under the conditions employed. Further application of the methodology to the corresponding gem-dialkoxy system was also explored to facilitate access to more complex carbocycles.

Selective Synthesis of Cyclooctanoids by Radical Cyclization of Seven-Membered Lactones: Neutron Diffraction Study of the Stereoselective Deuteration of a Chiral Organosamarium Intermediate

Seven-membered lactones undergo selective SmI2 -H2 O-promoted radical cyclization to form substituted cyclooctanols. The products arise from an exo-mode of cyclization rather than the usual endo-attack employed in the few radical syntheses of cyclooctanes. The process is terminated by the quenching of a chiral benzylic samarium. A labeling experiment and neutron diffraction study have been used for the first time to probe the configuration and highly diastereoselective deuteration of a chiral organosamarium intermediate.