SYNTHESIS OF (5,6-DIHYDRO-4H-PYRROLO[1,2-b]PYRAZOL-3-YL)METHANAMINE

This short paper reports the development of a new method for the synthesis of (5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)methanamine. Pyrazole was initially protected with an N-SEM protective group, followed by alkylation at C-5 position with 1-bromo-3-chloropropane. Following SEM deprotection, the intramolecular ring was closed and then a bromine atom (Br) was introduced with N-bromosuccinimide (NBS) by electrophilic aromatic substitution (SEAr), forming 3-bromo-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole. The Br group was subsequently converted into aldehyde group, then into oxime. The final step of hydrogenation resulted in the desired product. The overall yield through the 8-step reaction process was found to be 29.4%. The intermediates and final product were identified by HPLC-MS and H-1 NMR. This development provides a novel synthetic route to the formation of 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole skeleton.