Mechanochemical Metal-free N-Sulfonyl Transfer Reaction: Expedient Synthesis of N-Sulfonyl Amidines

An operationally simple mechanochemical reaction between iminoiodinanes with numerous cyclic 2(degrees)-amines such as morpholine, piperidine, pyrrolidine, thiomorpholine, N-Boc diazepine and N-Boc piperazine has been reported to afford N-sulfonyl amidines in moderate to excellent yield. The N-sulfonyl transfer reaction happens in a ball mill apparatus (RETSCH 400 (TM)) with three 5 mm stainless steel (ss) balls in a 5 mL stainless steel (ss) reaction jar with 2-methyl tetrahydrofuran as liquid assisted grinding auxiliary (LAG). This metal catalyst-base free synthesis with minimal solvents (as LAGs) demonstrated an efficient N-sulfonyl transfer reaction from iminoiodinanes. N-sulfonyl amidines are ubiquitous building blocks present in natural products and drug intermediates. Control experiments and computational studies based on density functional theory (DFT) calculations were performed to gain deeper insight into the mechanism.