An intramolecular transition-metal-free base-mediated hydroamination of propargylamine with isothiocyanates has been achieved. This atom-economical, regioselective intramolecular 5-exo-dig cycloisomerization was utilized for the one-pot synthesis of diversely substituted imidazole-2-thione and spiro-cyclic imidazolidine-2-thione. The reaction goes to completion at room temperature via propargylthiourea and 65-97% isolated yields were obtained.

Base-Mediated Hydroamination of Propargylamine: A Regioselective Intramolecular 5-exo-dig Cycloisomerization en Route to Imidazole-2-thione. -(RANJAN, A.; YERANDE, R.; WAKCHAURE, P. B.; YERANDE, S. G.; DETHE*, D. H.; Org. Lett. 16 (2014) 21, 5788-5791, http://dx.doi.org/10.1021/ol502871r ; Dep. Chem., Indian Inst. Technol., Kanpur 208 016, India; Eng.) -Mais 17-174

This paper describes a method for the racemization of unwanted (S)-1 isomer arising from the resolution of (±)-1. The process of racemization involves thiyl radical-mediated reversible hydrogen abstraction at the chiral center, in the presence of AIBN in water. The racemized isomer was subsequently resolved by L-(+)-tartaric acid to get (R)-1, a histamine H 3 receptor pharmacophore. We foresee that such an approach of racemization will be industrially useful for recycling waste (S)-1 enantiomer.

Herein we describe a sequential one‐pot multicomponent reaction for the synthesis of 2‐amino‐1,3‐selenazole. Amidinoselenourea synthesized from isoselenocyanate and N,N‐diethyl‐amidine reacted with various halomethylene compounds to furnish 2‐amino‐1,3‐selenazole derivatives in 65–89 % yields. The molecular structure of the trisubstituted selenazole formed was unambiguously established by X‐ray crystallography.

One-Pot Synthesis of 2-Amino-1,3-selenazole via an Intermediary Amidinoselenourea. -Amidinoselenoureas synthesized from isoselenocyanates and N,N-diethyl amidines reacts with halomethylene compounds to furnish 2-amino-1,3-selenazoles. -(RANJAN, A.; YERANDE, R.; JADHAV, M.; YERANDE*, S. G.; DETHE, D. H.; Eur. J. Org. Chem. 2015, 15, 3230-3234, http://dx.