Transition metal free synthesis of aryl thiocyanates aldehydes and ketones azaheterocyclic carboxamides and styrenyl ethers

Abstract

Oxidative C H functionalization to form new C C C N and C S bonds has emerged as an elegant and robust synthetic method for accessing useful products featuring atom economy and straightforwardness However many of these methods are based on transition metal catalysis which is usually associated with drawbacks such as cost toxicity and need for non commercial ligands As an alternative transition metal free versions have become very important for avoiding more expensive transition metal reagents and to tackle the environmental issues Potassium persulfate K2S2O8 has emerged as one of the powerful transition metal free reagents in organic synthesis It is relatively cheap environmentally friendly powerful oxidant and frequently used for the degradation of environmental and soil carbon pollutants It has also been widely used as a radical initiator in a number of industrial applications In this regard we focused our attention to explore the strength of K2S2O8 for the novel transition metal free protocols We developed an expedient and direct transition metal free regioselective thiocyanation of phenols anilines and heterocycles using NH4SCN and K2S2O8 Transformation is realized via the direct C H functionalization under transition metal free conditions at an ambient temperature in excellent yields Similarly we demonstrated a one pot protocol for the direct and clean transformation of aryl acetic acids to aldehydes and ketones in water using less expensive K2S2O8 as a reagent The protocol relies on the direct decarboxylation of sp3 hybridized carbon in water without any over oxidation into carboxylic acids with minimal waste Further we have developed a transition metal free carbamoylation of heterocycles using formamides NMF DMF and K2S2O8 The transformation is realized via direct dehydrogenative aminocarbonylation of heterocyclic compounds The method proved to be practical and a series of primary to tertiary carboxamides were synthesized without any side products We also developed a novel one pot transition m