Thiol-ene reactions involve the addition of a S-H bond across a double or triple bond by either a free radical or ionic mechanism. Thiol-ene reactions are essentially the sulfur version of the hydrosilylation reaction.
Because the reactions are efficient, high yielding, and tolerant of various solvents and functional groups, many researchers now consider the thiol-ene reaction to be a "click" reaction.
We have found the thiol-ene reaction to be an excellent method for derivatizing unsaturated organosilicon and organic compounds. We recently reported the synthesis of a variety of functional organosilicon compounds from thiol-ene reactions of tetravinylsilane with commercially available thiols. Representative examples are shown below. Yields ranged from 64 to 100%.
These compounds were prepared by irradiating solutions of tetravinylsilane and the thiol in open flasks. Ordinary borosilicate glassware can be used. Our light source was a simple sunlamp:
We are also investigating the application of these compounds as cores for divergent dendritic growth. Our results indicate that thioether dendrimers up to the fifth generation can be prepared using thiol-ene chemistry (3rd generation dendrimer shown below).
We have used the carbosilane-thioether dendrimers to stabilize Ag nanoparticles through chemical reduction, UV irradiation, or simple heating.
Using ionic thiol-ene (thiol-Michael) chemistry, we derivatized 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) in high yields and short reaction times. Very little purification of the products was necessary.
We obtained good quality single crystals of one of the products. The X-ray crystal structure indicated the formation of capsule-like dimers connected in a linear chain. Hydrogen bonding plays an important role in the solid state structure.
We are currently investigating the application of these and related compounds as chelating ligands and ion recognition agents. We have also extended this chemistry to the synthesis of star-shaped oligomers, again using TAT as a core.
We recently discovered a route to multifunctional thiols through the selective reaction of mercaptoalcohols with chlorosilanes. Representative examples are shown below. Yields were generally good to excellent.
Through a collaboration with Professor Walter Voit at the University of Texas at Dallas, these multi-thiols are being used for the preparation of degradable thiol-ene substrates.