共查询到20条相似文献,搜索用时 15 毫秒
1.
Khadija Gambouz Mohsine Driowya Mohammed Loubidi Zahira Tber Hassan Allouchi Saïd El Kazzouli Mohamed Akssira Grald Guillaumet 《RSC advances》2019,9(50):29051
A multicomponent reaction giving easy and cheap access to a variety of bicyclic 5,5-fused hetero-rings has been developed. Then, an usual rearrangement of imidazo[1,5-a]imidazoles or imidazo[1,2-b]pyrazoles leading to bi-heterocyclic imidazo- and pyrazolo[1,5-a]pyrimidines in the presence of a specific amount of I2 in THF at room temperature has been achieved. This new method enables the hitherto unreported synthesis of functionalized imidazo- and pyrazolo[1,5-a]pyrimidines.A multicomponent reaction giving easy and cheap access to a variety of bicyclic 5,5-fused hetero-rings has been developed. 相似文献
2.
A novel Mg3N2-assisted one-pot annulation strategy has been developed via cyclo-condensation reaction of 2-pyridyl ketones with alkyl glyoxylates or aldehydes, allowing the formation of imidazo[1,5-a]pyridines exclusively with an exellent yield.A novel Mg3N2-assisted one-pot annulation strategy has been developed via cyclo-condensation reaction of 2-pyridyl ketones with alkyl glyoxylates or aldehydes, allowing the formation of imidazo[1,5-a]pyridines exclusively with an exellent yield. 相似文献
3.
Because the majority of cancers exhibit direct or indirect deregulation of cyclin-dependent kinase (CDK) function, members of the CDK family are attractive targets for the development of anticancer agents. As part of an ongoing program, novel imidazopyridines were identified and developed as potent and selective CDK inhibitors. Here, we describe data on the in vitro biological activities of one of these compounds, AZ703. The selectivity profile of AZ703 was investigated in kinase assays against a range of CDK enzymes as well as a panel of protein kinases in vitro. IC50s were assessed against different tumor cell lines in vitro. The mechanism of action of AZ703 was determined by observing changes in phosphorylation of CDK substrates and cell cycle effects on tumor and normal cells. In vitro studies revealed that AZ703 is a selective inhibitor of CDK1 and CDK2 and displays a mode of action consistent with the induction of G1-, S-, and G2-M-phase arrest. AZ703 also showed potent antiproliferative activity across a wide range of tumor cell lines in vitro. Moreover, AZ703 induced reversible blockade of normal cells while causing tumor cells to undergo apoptosis. We have identified AZ703 as a novel selective imidazo[1,2-a]pyridine CDK inhibitor that shows promising antitumor properties in vitro. 相似文献
4.
Rasapalli Sivappa Vamshikrishna Reddy Sammeta Yanchang Huang James A. Golen Sergey N. Savinov 《RSC advances》2019,9(51):29659
A facile entry to 3-aryl/alkenyl/alkynyl substituted imidazo[1,2-a]pyridines (3a–p, 6a–d & 9a–9e) has been developed from readily available benzyl/allyl/propargyl halides and 2-amino pyridines as substrates via formimidamide chemistry that is devoid of caustic or expensive reagents, such as transition metal complexes. Quantum chemical calculations performed to understand the underlying mechanism of the transformation revealed a preference for intramolecular Mannich-type addition over pericyclic 1,5-electrocyclization for the systems reported herein that enable a Baldwin allowed 5-exo-trig cyclization instead of a formally anti-Baldwin 5-endo-trig process.A facile entry to 3-substituted imidazo[1,2-a]pyridines from halides and 2-amino pyridines via formimidamide chemistry has been developed through a formal anti-Baldwin 5-endo-trig cyclization that becomes a thermally allowed 5-exo-trig cyclization. 相似文献
5.
Ryan Q. Tran Seth A. Jacoby Kaitlyn E. Roberts William A. Swann Nekoda
W. Harris Long P. Dinh Emily L. Denison Larry Yet 《RSC advances》2019,9(31):17778
3-Aryl-2-phosphinoimidazo[1,2-a]pyridine ligands were synthesized from 2-aminopyridine via two complementary routes. The first synthetic route involves the copper-catalyzed iodine-mediated cyclizations of 2-aminopyridine with arylacetylenes followed by palladium-catalyzed cross-coupling reactions with phosphines. The second synthetic route requires the preparation of 2,3-diiodoimidazo[1,2-a]pyridine or 2-iodo-3-bromoimidazo[1,2-a]pyridine from 2-aminopyridine followed by palladium-catalyzed Suzuki/phosphination or a phosphination/Suzuki cross-coupling reactions sequence, respectively. Preliminary model studies on the Suzuki synthesis of sterically-hindered biaryl and Buchwald–Hartwig amination compounds are presented with these ligands.3-Aryl-2-phosphoimidazo[1,2-a]pyridine ligands were prepared via two complimentary synthetic routes and were evaluated in the Suzuki–Miyaura and Buchwald–Hartwig amination cross-coupling reactions.Palladium-catalyzed cross-coupling reactions have revolutionized the formation of C–C and C–X bond formation in the academic and industrial synthetic organic chemistry sectors.1,2 Applications such as synthesis of natural products,3 active pharmaceutical ingredients (API),4 agrochemicals,5 and materials for electronic applications6 are showcased. Snieckus described in his 2010 Nobel Prize review that privileged ligand scaffolds represented the “third wave” in the cross-coupling reactions where the “first wave” was the investigation of the metal catalyst-the rise of palladium and the “second wave” was the exploration of the organometallic coupling partner.1 In the last twenty years, it was recognized that the choice of ligand facilitated the oxidative addition and reductive-elimination steps of the catalytic cycle of transition metal-catalyzed cross-coupling reactions, increasing the overall rate of the reaction. For example, bulky trialkylphosphines facilitated the oxidative addition processes of electron-rich, unactivated substrates such as aryl chlorides.7,8 Sterically demanding ligands also provided enhanced rates of reductive elimination from [(L)nPd(aryl)(R), R = aryl, amido, phenoxo, etc.] species by alleviation of steric congestion.9 Privileged ligands such as Buchwald''s biarylphosphines,10,11 Fu''s trialkylphosphines,7,8,12 Nolan–Hermann''s N-heterocyclic carbenes (NHC),13–15 Hartwig''s ferrocenes,16,17 Beller''s bis(adamantyl)phosphines18,19 and N-aryl(benz)imidazolyl or N-pyrrolylphosphines,20,21 Zhang''s ClickPhos ligands,22,23 and Stradiotto''s biaryl P–N phosphines,24,25 to mention a few, have found wide-spread use in Suzuki–Miyaura, Corriu–Kumada, Heck, Negishi, Sonogashira, C–X (X = S, O, P) cross-coupling and Buchwald–Hartwig amination reactions (Fig. 1). Preformed catalysts with these ligands attached to the palladium metal center are also recognized as well-defined entities in cross-coupling reactions.26Open in a separate windowFig. 1Privileged ligands for palladium-catalyzed cross-coupling reactions.The term privileged structure was first coined by Evans et al. in 1988 and was defined as “a single molecular framework able to provide ligands for diverse receptors”.27 In the last three decades, it is clear that privileged structures are exploited as opportunities in drug discovery programs.28–31 For example, imidazo[1,2-a]pyridines are privileged structures in medicinal chemistry programs (Fig. 2).32 Imidazo[1,2-a]pyridines are a represented motif in several drugs on the market such as zolpidem, marketed as Ambien™ for the treatment of insomnia,33 minodronic acid, marketed as Bonoteo™ for oral treatment of osteoporosis,34 and olprinone, sold as Coretec™ as a cardiotonic agent.35Open in a separate windowFig. 2Imidazo[1,2-a]pyridines as privileged structures in medicinal chemistry and in our cross-coupling reactions approach.Our group is interested in a long-term research program directed at the use of key privileged structures that are employed in drug discovery programs as potential phosphorus ligands for cross-coupling reactions. In our entry into the use of privileged structures from the medicinal chemistry literature for our investigation into new phosphorus ligands, we have developed two complementary synthetic routes for the preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands from 2-aminopyridine as our initial substrate.Our first synthetic route for the preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands 3a–3l required the copper(ii) acetate iodine-mediated double oxidative C–H amination of 2-aminopyridine (1) with arylacetylenes under an oxygen atmosphere to give 3-aryl-2-iodoimidazo[1,2-a]pyridines 2a–2d (Scheme 1).36,37Open in a separate windowScheme 1Preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands 3a–3l from 2-aminopyridine via copper-catalyzed arylacetylene cyclizations/palladium-catalyzed phosphination reactions sequences.Phenylacetylene and 2-/3-/4-methoxyphenylacetylenes were commercially available reagents. With intermediates 2a–d in hand, we explored several cross-coupling phosphination reactions and we found that palladium-catalyzed phosphination with DIPPF ligand in the presence of cesium carbonate as the base in 1,4-dioxane under reflux provided twelve new ligands 3a–3l as shown in 38 Moderate to good yields were obtained under these cross-coupling conditions. There are few commercially available dimethoxyphenylacetylenes, and most are prohibitively expensive, and so an alternative synthetic strategy was explored.Palladium-catalyzed phosphination of 3-aryl-2-iodoimidazo[1,2-a]pyridines 2a–2da
Open in a separate windowaReaction conditions: 2a–2d (1 equiv.), HPR2 (1 equiv.), Pd(OAc)2 (2 mol%), Cs2CO3 (1.2 equiv.), DIPPF (2.5 mol%), 1,4-dioxane, 80 °C.2-Iodoimidazo[1,2-a]pyridine (4) was conveniently prepared in three steps from 2-aminopyridine (1) following literature procedures, which was then converted into either iodo 5 or bromo 6 with NIS or NBS, respectively (Scheme 2).39,40Open in a separate windowScheme 2Preparation of 2,3-diiodoimidazo[1,2-a]pyridine (5) and 3-bromo-2-iodoimidazo[1,2-a]pyridine (6).When the phosphorus ligands 3 contained tert-butyl or cyclohexyl groups, method 1 was followed where 2,3-diiodoimidazo[1,2-a]pyridine (5) underwent Suzuki cross-coupling reactions with arylboronic acids to yield aryl intermediates 7a–7f, which was followed by palladium-catalyzed cross-coupling phosphination reactions with di-tert-butylphosphine or dicyclohexylphosphine to give C-2 substituted phosphorus ligands 3m–3u in low to moderate yields (Scheme 3, 38 The phosphorus ligands 3v–3ab were prepared from 3-bromo-2-iodoimidazo[1,2-a]pyridine (6) via a palladium-catalyzed phospination with diphenylphosphine (method 2) to give intermediate 8 (X = Br, I becomes PPh2) followed by Suzuki palladium-catalyzed cross-coupling reactions with arylboronic acids. Note that the change in reactivity of the core when switching between bromo and iodo at C3 results in a change in the order of cross-coupling steps.Open in a separate windowScheme 3Preparation of 3-aryl-2-phosphinoimidazo[1,2-a]pyridine ligands 3m–3ab from 2-iodo-3-iodo(or bromo)imidazo[1,2-a]pyridines 5 or 6via palladium-catalyzed Suzuki/phosphination or a phosphination/Suzuki cross-coupling reactions sequences.Palladium-catalyzed Suzuki/phosphination or phosphination/Suzuki reactions sequences of 2,3-diiodoimidazo[1,2-a]pyridine (5) or 3-bromo-2-iodoimidazo[1,2-a]pyridine (6)a
Open in a separate windowaReaction conditions: 5, ArB(OH)2, Pd(PPh3)4 (5 mol%), Na2CO3 (2 equiv.), 1,4-dioxane/H2O (2 : 1) and HPR2 (1 equiv.), Pd(OAc)2 (2.5–5 mol%), Cs2CO3 (1.2 equiv.), DIPPF (2.5–10 mol%), 1,4-dioxane, 80 °C or 6, reverse sequence of reactions.With our library of functionalized imidazo[1,2-a]pyridine phosphorus ligands 3a–3ab in hand, we began to screen these ligands in Suzuki–Miyaura cross-coupling reactions to prepare sterically-hindered biaryl compounds. We chose the Suzuki–Miyaura cross-coupling reactions of m-bromo-xylene (9) and 2-methoxyphenylboronic acid (10) to give 2,6-dimethyl-(2-methoxy)biphenyl (11) as our model reaction as outlined in ii) acetate with 2.5 equivalents of base in 1,4-dioxane at 80 °C for 12–24 h. As expected, SPhos and XPhos were employed as our initial ligands to confirm our GC analyses of >99% conversion in our chosen model reaction (Entries 14–15). With the GC conditions validated, we screened selected ligands from 3a–3ab. It was clearly evident that the di-tert-butyl phosphorus ligands represented by 3a, 3m, and 3p were ineffective ligands in our model reactions (Entries 1–3). Furthermore, the diphenyl phosphorus ligands such as 3w, 3y, 3z, and 3ab showed low to moderate conversions in the model cross-coupling reactions (Entries 6–9). However, the dicyclohexyl phosphorus ligands shown by 3r and 3t showed greater than 99% conversions by GC analyses (Entries 4–5). Further exploration of ligand 3r with K3PO4 as the base, stirring the reaction overnight at room temperature or for 3 h at 80 °C showed inferior conversions (Entries 10–12). There was no conversion when a ligand was not used in the model reaction (Entry 13).Optimization of conditions for the Suzuki–Miyaura cross-coupling model reaction
Open in a separate windowaBased on GC analyses of consumed 9.bIsolated yield of 96% was obtaisned.Furthermore, a Buchwald–Hartwig amination model study was investigated with our new imidazo[1,2-a]pyridine phosphorus ligands 3a–3ab. The Buchwald–Hartwig amination reaction of 4-chlorotoluene (12) with aniline (13) to give 4-methyl-N-phenylaniline (14) was screened with our ligands ( Entry Ligand Conditions Conversiona (%) 1 3a 38 2 3d 26 3 3e >99 b 4 3g 29 5 3h 54 6 3k 71 7 3n 0 8 3p 0 9 3q >99 10 3r 92 11 3s >99 12 3s K3PO4 was used as base 83 13 3s K2CO3 was used as base 0 14 3s KOt-Bu was used as base >99 15 3s NaOt-Bu was used as base >99
Entry | Ar | R | 3 (% yield) |
---|---|---|---|
1 | Ph (2a) | t-Bu | 3a (41) |
2 | Ph (2a) | Cy | 3b (50) |
3 | Ph (2a) | Ph | 3c (61) |
4 | 2-OMeC6H4 (2b) | t-Bu | 3d (53) |
5 | 2-OMeC6H4 (2b) | Cy | 3e (83) |
6 | 2-OMeC6H4 (2b) | Ph | 3f (69) |
7 | 3-OMeC6H4 (2c) | t-Bu | 3g (62) |
8 | 3-OMeC6H4 (2c) | Cy | 3h (72) |
9 | 3-OMeC6H4 (2c) | Ph | 3i (79) |
10 | 4-OMeC6H4 (2d) | t-Bu | 3j (73) |
11 | 4-OMeC6H4 (2d) | Cy | 3k (55) |
12 | 4-OMeC6H4 (2d) | Ph | 3l (59) |
Entry | R | Ar | Method/substrate | Step 1 (% yield) | Step 2 (% yield) |
---|---|---|---|---|---|
1 | t-Bu | 2,3-diOMeC6H3 | 1, 5 | 7a (59) | 3m (64) |
2 | t-Bu | 3,4-diOMeC6H3 | 1, 5 | 7b (54) | 3n (31) |
3 | t-Bu | 2,5-diOMeC6H3 | 1, 5 | 7c (58) | 3o (61) |
4 | t-Bu | 3,4,5-triOMeC6H2 | 1, 5 | 7d (50) | 3p (62) |
5 | Cy | 2,3-diOMeC6H3 | 1, 5 | 7a (59) | 3q (46) |
6 | Cy | 2,6-diOMeC6H3 | 1, 5 | 7e (40) | 3r (52) |
7 | Cy | 3,4-diOMeC6H3 | 1, 5 | 7b (54) | 3s (52) |
8 | Cy | 2,3,4-triOMeC6H2 | 1, 5 | 7f (58) | 3t (21) |
9 | Cy | 3,4,5-triOMeC6H2 | 1, 5 | 7d (50) | 3u (55) |
10 | Ph | 2,3-diOMeC6H3 | 2, 6 | 8 (70) | 3v (52) |
11 | Ph | 2,5-diOMeC6H3 | 2, 6 | 8 (70) | 3w (68) |
12 | Ph | 3,4-diOMeC6H3 | 2, 6 | 8 (70) | 3x (67) |
13 | Ph | 2,3,4-triOMeC6H2 | 2, 6 | 8 (70) | 3y (52) |
14 | Ph | 3,4,5-triOMeC6H2 | 2, 6 | 8 (70) | 3z (64) |
15 | Ph | 4-FC6H4 | 2, 6 | 8 (70) | 3aa (40) |
16 | Ph | 3-F,5-OMeC6H3 | 2, 6 | 8 (70) | 3ab (39) |
Entry | Ligand | Conditions | Conversiona (%) |
---|---|---|---|
1 | 3a | 12 | |
2 | 3m | 20 | |
3 | 3p | 14 | |
4 | 3r | >99 b | |
5 | 3t | >99 | |
6 | 3w | 21 | |
7 | 3y | 55 | |
8 | 3z | 46 | |
9 | 3ab | 11 | |
10 | 3r | K3PO4 was used as base reaction was performed at 25 °C reaction was stirred for 3 h no ligand | 91 |
11 | 3r | 4 | |
12 | 3r | 39 | |
13 | — | 0 | |
14 | SPhos | >99 | |
15 | XPhos | >99 |