Light-Induced Metal-Free Generation of Cyanocarbenes from Alkynyl Triazenes for the Synthesis of Nitrile Derivatives.

The chemistry of alkynyl triazenes is an emerging field for organic chemists and especially acid-induced nucleophilic functionalizations, either directly, or after a prior reaction towards aromatic triazenes under extrusion of nitrogen, paved the way for fruitful strategies. In contrast, the chemical behavior of alkynyl triazenes upon irradiation with light is still unknown. Herein we present the first photoactivation of alkynyl triazenes that triggers an uncommon reactivity pattern involving the cleavage of the N1-N2 bond of the triazene moiety resulting in a unique approach to cyanocarbenes from a readily available, stable, and insensitive precursor. This allows to access various nitrile compounds without the use of a toxic cyanating agent by exploiting the reactivity pattern of carbenes. By variation of the reaction conditions and light sources, different substitution patterns can be obtained selectively in good yields under mild and metal-free conditions, thus introducing the alkynyl triazene unit as a photo accessible methylene nitrile synthon. Using this synthon, subclasses like α-alkoxynitriles, α-aminonitriles and α-cyanohydrazones become easily available. These exhibit synthetically valuable substitution patterns for the synthesis of pharmaceuticals, intermediates for total synthesis and amino acid synthesis.

Guanidines from 'toxic substances' to compounds with multiple biological applications--detailed outlook on synthetic procedures employed for the synthesis of guanidines.

Guanidines to begin with, were thought of being harmful substances associated with medical ailment. With the advent of World War I and the impact it left on the populations at large research focus was shifted, towards polymer synthesis and that too on plastics and rubbers which were mostly employed in various artillery equipments. In the surge, to get plastics and rubbers with enhanced mechanical properties, many variedly substituted guanidines used as accelerators in vulcanization of polymers were synthesized using different procedures. Continuous research on guanidines, led scientists to develop different protocols and routes for the synthesis of these compounds, later these were tested for their possible use in various areas and now these are sought for their enhanced biomedical and catalytic applications. This review article presents thirty six different synthetic procedures employed for the synthesis of guanidines over the years including seventy schemes and a brief account on the reported wide ranging applications of some novel guanidines.