Lity.9 The promising indolyl drug pruvanserin (3, selective 5-HT2A serotonin receptor
Lity.9 The promising indolyl drug pruvanserin (3, selective 5-HT2A serotonin receptor antagonist)102 has been discontinued in phase II clinical trials as a drug for the treatment of insomnia.13 The corresponding 1Himidazo[1,2-b]pyrazole isostere 4 was predicted to display improved solubility in physiological media. We consequently have created a toolbox allowing the selective functionalization ofthe 1H-imidazo[1,2-b]pyrazole skeleton, which enabled the preparation of the pruvanserin isostere four in an effort to compare the physicochemical properties on the matched pair three and 4 (Fig. two). Previously reported protocols for the preparation of 1H-imidazo[1,2-b]pyrazoles require the synthesis of new beginning components for each and every functionalized derivative, as the ring fusion is only MEK Inhibitor Storage & Stability achieved in the nal actions.147 To avoid this situation, we have selected a synthetic strategy involving a successive and selective functionalization with the readily out there 1H-imidazo [1,2-b]pyrazole scaffold. Hence, we envisioned to employ a Br/Mg-exchange also as selective magnesiations and zincations employing metal amides. Previously, we’ve got reporteda Division Chemie, Ludwig-Maximilians-Universit�t M�nchen, Munich 81377, a u Germany. E-mail: [email protected] bGlobal Discovery Chemistry, Novartis Institutes of BioMedical Research, Basel 4057, SwitzerlandElectronic supplementary information and facts (ESI) offered: Deposition quantity 2097280 (7a) contains the supplementary crystallographic information for this paper. CCDC 2097280. For ESI and crystallographic information in CIF or other electronic format see DOI: ten.1039/d1sc04155jFig.Examples of 1H-imidazo[1,2-b]pyrazoles with biological activities.2021 The Author(s). Published by the Royal Society of ChemistryChem. Sci., 2021, 12, 129933000 |Chemical ScienceEdge Report Herein, we report such a selective functionalization sequence starting using the two readily obtainable 7-brominated, SEM-protected 1H-imidazo[1,2-b]pyrazoles 5a and 5b 15 (Scheme 1). Initial, a Br/Mg-exchange with iPrMgCl LiCl (6),18 followed by trapping reactions with numerous electrophiles, yielded monosubstituted 1H-imidazo[1,2-b]pyrazoles of type 7. Two further functionalizations inside the 3- and 2-positions were achieved via consecutive metalations with TMPMgCl LiCl (8),20 and TMP2Zn MgCl2 2LiCl (9).21 Subsequent quenching reactions with different electrophiles then gave access to the increasingly functionalized 1H-imidazo[1,2-b]pyrazoles of variety 10 and 11 respectively. Aer deprotection of your SEM-group, a Nheterocyclic compound of variety 12 was obtained. Additionally, we report a mild fragmentation from the pyrazole ring247 in functionalized 1H-imidazo[1,2-b]pyrazoles of variety 11 induced by metalation at the 6-position with TMP2Zn MgCl2 2LiCl (9) (Scheme 2). This reaction proceeded through zincated intermediates of form 13 and led to a series of (1,3-dihydro-2H-imidazol-2-ylidene)malononitriles of kind 14. Although some (1,3-dihydro-2H-imidazol-2-ylidene) malononitriles were currently reported,28,29 this fragmentation supplied an entry to several different newly functionalized derivatives of form 14. This functional group diversity was crucial for tuning the uorescent properties of the push ull dyes 14.30 Lastly, we report a concise synthesis of the 1H-imidazo[1,2b]pyrazole isostere 4 of pruvanserin too as an experimental evaluation of its physicochemical properties in comparison to the original drug (3).1H-Imidazo[1,2-b]pyrazole (1) as a potential replacement of μ Opioid Receptor/MOR Inhibitor Synonyms indole (two).