Design, synthesis, and applications of novel phenyl/acetylenic cyclophanes.

Abstract

The synthesis of a novel family of acetylenic cyclophanes via Pd, Cu and Zn catalyzed cross-coupling reactions is described. The cyclophanes were constructed in good yields and X-ray crystal analysis revealed a twisted helical geometry. The nature of the geometry and the ability to complex solvent molecules within the lattice varied upon the number of acetylenic linkages present. Functionalized cyclophanes bearing long alkyl chains based on the helical structures 191 and 213 were also synthesized with potential as novel liquid crystals. Cyclophane 280 showed LC-like behavior when melting was observed under a polarized light microscope. Intramolecular cyclization of paracyclophanes was observed and resulted in cyclophanes, 192 and 203. X-ray crystallographic analysis of the carboxylic acid derivative, 203 revealed the strained nature of the butadiyne bridge. The triple bonds were distorted with bond angles of 163.7° and 163.5°. A novel method for the synthesis of diynes and tetraynes using an in situ desilylation/dimerization procedure was developed but was unsuccessful in producing linear hexaynes. Attempted dimerization of 281 for the synthesis of 282 failed due to a competing intramolecular producing 283. Derivative 307 revealed another highly strained butadiyne bridge possessing bond angles of 164.1° and 153.4°. Metacyclophanes with a termini separation of approximately between 7.8 and 10 A did not undergo intramolecular cyclization. A sequential coupling procedure involving a double dimerization of acetylenes produced traces of the desired cyclophane 282 and no competing intramolecular cyclization products were observed. Progress towards 327, a structural isomer of 282, using an alternative sequential coupling protocol involving a double Sonogashira cyclization is detailed. Attempts to prepare acetylenic cyclophanes bearing metaphenyl/acetylene linkages are described. Initial investigations into the incorporation of thiophenes to acetylenic cyclophanes were thwarted by the instability of the precursor, 372.* *Please refer to dissertation for diagram.