Squeezing Out the Catalysts: A Sustainable Approach to Disulfide Bond Exchange in Aryl Disulfides

Abstract

High-pressure conditions can be considered as an alternative, environmentally responsible way for the equilibrium reactions, such as disulfide exchange. This approach is capable of eliminating the catalysts or stimuli, such as reducing agents, strong bases, ultraviolet light, or ultrasound. The exchange of aryl disulfides in the absence of catalysts or other stimuli has been systematically studied. The effects of pressure in the range between 100 and 400 MPa, accessible in large-scale technological installations, have been tested for promoting exchange reactions between various homodimeric aryl disulfides. For the optimized conditions, 100% yields of the heterodimer in pure single-crystal form were obtained. The reactions were performed in a diamond anvil cell, as well as in a hydraulic piston-and-cylinder press, and the products were characterized by X-ray diffraction, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The prominent role of high-entropy states, not attainable under ambient conditions, as well as the high-entropy nucleation, kinetic crystallization, and other effects associated with the high-pressure environment, has been demonstrated. These entropy-driven reactions represent an efficient, environmentally friendly, one-pot method for obtaining pure crystalline heterodimeric disulfides.

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