Creation of Novel Toxic Gas Surrogates and the Development of Safe and Facile Catalytic Reactions

Abstract

The use of toxic gas surrogates in organic reactions instead of the gas itself contributes to enhancing the safety, practicality, and efficiency of the reactions involved. Our efforts toward the creation of toxic gas surrogates and the development of a series of catalytic reactions using these surrogates are described. Improvements in substrate scope during the hydroesterification of alkenes using formates facilitated by the Ru–imidazole catalyst system provided the opportunity to discover that phenyl formate is a useful carbon monoxide (CO) surrogate for the generation of CO and phenol under weakly basic conditions. This discovery triggered the development of highly reactive but stable CO surrogates and a variety of Pd-catalyzed carbonylative transformations. N-Formylsaccharin facilitated the use of additional nucleophiles in carbonylation reactions that provided access to a variety of carbonyl compounds. Detailed experimental and theoretical mechanistic studies into the generation of CO from phenyl formate suggest that CO generation proceeds via a concerted E2 α-elimination. Furthermore, a known surrogate of sulfur dioxide was applied for the first time to the selective syntheses of cyclic sulfonamides and sulfinamides, confirming that the surrogate operates as an “S=O” source. Notably, the reactions described herein are scalable and can be performed without the use of external toxic gases and specialized reaction vessels; they are easy and simple to perform and demonstrate enormous potential for industrial application.

Graphical Abstract