Devesh M. Sawant

Ruthenium Catalyzed Intramolecular C–S Coupling Reactions: Synthetic Scope and Mechanistic Insight

A ruthenium catalyzed intramolecular C-S coupling reaction of N-arylthioureas for the synthesis of 2-aminobenzothiazoles has been developed. Kinetic, isotope labeling, and computational studies reveal the involvement of an electrophilic ruthenation pathway instead of a direct C-H activation. Stereoelectronic effect of meta-substituents on the N-arylthiourea dictates the final regioselective outcome of the reaction.

Pictet-Spengler Reaction Revisited: Engineering of Tetherd Biheterocycles into Annulated Polyheterocycles

This micro review focuses on the application of the modified Pictet-Spengler reaction to the synthesis of diverse polyheterocy- cles with structural resemblance to natural products. The modified Pictet-Spengler reaction takes use of tethered biheterocycles compris- ing nucleophilic partner and a source for electrophilic partner followed by their condensation with aldehydes/ketones to furnish annulated polyheterocycles. Using this strategy engineering of numerous tethered biheterocycles into annulated polyheterocycles has been success- fully carried out using both 6-endo as well as 7-endo cyclizations.

A catalyst-free, one-pot multicomponent synthesis of spiro-benzimidazoquinazolinones via a Knoevenagel–Michael-imine pathway: a microwave assisted approach

A novel multi-component route for the synthesis of spiro-benzimidazoquinazolinones has been developed under microwave irradiation. It involves a one-pot three-component reaction of acenaphthoquinone or isatin, 1,3-diketone and 2-aminobenzimidazole in ethanol at 180 W and 160 °C temperature. An attractive feature of this method is the mild conditions with operational simplicity. The computational studies provide insight into the mechanistic aspects of the reaction.

Ruthenium-Catalyzed Oxidative C–H Bond Alkenylation of 2-Phenylimidazo[1,2-a]pyridine

Monoalkenylation of sp 2 C–H bonds directed by the innate reactivity of imidazo[1,2- a ]pyridine to afford 2-(2′-alkenylphenyl)imidazo[1,2- a ]pyridine with high levels of diastereoselectivity is described. The methodology is employed to generate di-substituted alkenes by using a cationic ruthenium(II) catalyst in the presence of AgSbF 6 and Cu(OAc) 2 ·H 2 O under air.

Sequential Pd(0)/Fe(III) Catalyzed Azide–Isocyanide Coupling/Cyclization Reaction: One-Pot Synthesis of Aminotetrazoles

A rapid and efficient synthesis of aminotetrazole from aryl azides, isocyanides, and TMSN3 is developed. The reaction is promoted by sequential Pd(0)/Fe(III) catalysis. The reaction sequence utilizes the Pd-catalyzed azide-isocyanide denitrogenative coupling reaction to generate unsymmetric carbodiimide in situ, which reacts with TMSN3 in the presence of FeCl3 in a single pot. The methodology has distinct advantages over traditional synthetic approaches where toxic Hg and Pb salts are employed at stoichiometric scale.