Synthesis of new tetrathia[7]helicene-based gold (I) complexes

Tetrathia[7]helicenes (7-TH) are polyconjugated -systems in which four thiophene rings are orthofused to alternating arene rings to generate a non planar, chiral, stable helix which allows the existence of M and P enantiomers. The 7-TH systems are very interesting structures1 even because they can be easily and selectively functionalized in the alpha positions of the terminal thiophene rings,2 making it possible the introduction of appropriate substituents. In the course of our studies on the synthesis of phosphane derivatives of 7-TH as potential innovative chiral ligands in stereoselective organometallic catalysis,3 novel gold(I) complexes of the mono and bidentate phosphine of 7,8-di-n-propyl-tetrathia[7]helicene have been synthesized (Scheme 1) and tested in some model carbon-carbon bond forming reactions.The use of gold in homogeneous catalysis has witnessed tremendous activity in recent years.4 In fact, thanks to gold(I) phosphine-based catalysts, various organic transformations have been accessible with both high yields and chemo- and stereoselectivity.