Quadruple Functionalization of a Tetraphenylethylene Aromatic Scaffold with Ynamides or Tetracyanobutadienes: Synthesis and Optical Properties

Abstract

Ynamides are useful and versatile building blocks in organic synthesis, from which 1,1,4,4-tetracyanobutadienes (TCBD) can be prepared for application in molecular electronics. However, their insertion onto multi-functional molecular scaffold remains a synthetic challenge. In this work, we report the two-steps synthesis in good isolated yield (64 % overall, 89 % stepwise) of a tetraphenylethylene (TPE) bearing four ynamides, and its further one-step conversion into the tetra-TCBD derivative through a [2+2] cycloaddition-retroelectrocyclization sequence. The concomitant formation of the four ynamides required a specific optimisation of the reaction conditions. Although a poor fluorescent emitter in solution, the tetra-TCBD compound displayed near-infrared luminescence in the solid state, which is an attractive optoelectronic feature when considering future applications in molecular electronic devices.