Recent advances in the transition metal catalyzed carbonylation of alkynes, arenes and aryl halides using CO surrogates
Transition metal catalyzed carbonylation reactions using carbon monoxide as the C-1 source have occupied an all important position in catalysis which is subsequently related to organic synthesis and industrial synthesis of molecules. However, the use of carbon monoxide, an inflammable, toxic greenhouse gas acts as a deterrent to academic and industrial research. Hence, it is imperative to develop a CO-free protocol for promoting sustainable chemistry. The chemistry of CO surrogates has undergone substantial progress with the development of newer reaction methodologies and newer surrogate molecules. Aldehydes, formate esters, formamides, and metal carbonyls have been applied not only to the synthesis of industrial bulk chemicals, but also to the synthesis of specialty chemicals and molecules which are important pharmacological building blocks. Simultaneous development of a two-chamber reactor allows for the ex situ generation of CO and hence circumvents the compatibility issues associated with the substrate and the surrogate during in situ CO generation. Further, the development of specialized surrogate molecules allows for the incorporation of 13C and 14C-labelled isotopes even at an advanced stage of the synthesis of the molecules. This review thus summarizes the progress in the past decade in the development of synthetic methodologies in which carbonylation reactions are carried out without the use of gaseous carbon monoxide or using carbon monoxide surrogates.