Stereoselective Wittig Olefination as a Macrocyclization Tool. Synthesis of Large Carbazolophanes

J Org Chem. 2015 Jun 19;80(12):6300-12. doi: 10.1021/acs.joc.5b00745. Epub 2015 Jun 4.

Abstract

Z-Selective Wittig olefination was applied to the synthesis of large carbazolophanes containing up to eight heteroaromatic subunits. A number of strategies were devised and tested, showing that cyclooligomerization yields can be significantly improved by using one-component schemes involving heterobifunctional reactants. [4]- and [6]Carbazolophanes were characterized in the solid state, revealing compact, highly folded structures. Electronic and steric effects of substitution and chain length on the Wittig olefination rates and Z-selectivities were explored theoretically using DFT calculations.