Improved Thiourea Catalysts (20150314, Dr. Steven Kass)
Metal-free, Mono-Charged Thiourea
A series of new, powerful thiourea catalysts show significant improvement in activity over Schreiner’s thiourea, the industry standard, in carrying out organic transformations. Higher activity allows for lower catalyst loadings, lower reaction temperatures, higher selectivities and the ability to induce transformations that less reactive catalysts cannot. These metal-free mono-charged thioureas and dicationic salts are also non-corrosive, air/water stable and environmentally friendlier than metal-containing catalysts.
Faster Friedel-Crafts Reaction
In a Friedel-Crafts reaction using a new mono-charged thiourea, the reaction speed showed a six-fold improvement in activity over the same reaction catalyzed by Schreiner's thiourea. In addition, a new dicationic salt catalyst reduced the reaction half-life to only 4.8 minutes, a 350-fold improvement over the 28.4 hour half-life with Schreiner's thiourea. Furthermore, the reaction was nearly 96% complete in only 25 minutes compared to over 121 hours with Schreiner’s thiourea.
Reduced Diels-Alder Reaction Time
A Diels-Alder reaction catalyzed by Schreiner's thiourea demonstrated a reaction half-life of 1.6 hours. In contrast, the new mono-charged thiourea decreased the half-life to 15 minutes (20-fold acceleration) and the dicationic salt reduced it further to only 1.8 minutes (180-fold acceleration).
BENEFITS AND FEATURES OF CHARGE-ENHANCED THIOUREA CATALYSTS:
- Six- to 350-fold improvement in activity over Schreiner’s thiourea, the industry standard
- Catalysts are metal-free, inexpensive and easier to synthesize
- Non-toxic, non-corrosive, and air/water stable
- Allows for lower catalyst loadings, lower reaction temperatures and higher selectivities
- Able to induce transformations not possible with less reactive catalysts
- Catalysts could find use in a wide variety of commercial and industrial processes
Phase of Development - Proof of Concept