AR T I C L E

Efficient synthesis and In Silico study of some novelpyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives

Fathy M. Abdelrazek1,2 | Sobhi M. Gomha1,3 | Hassan M. Abdel-aziz4 |

Mohamed S. Farghaly1,5 | Peter Metz2 | Ahmed Abdel-Shafy1

1Chemistry Department, Faculty ofScience, Cairo University, Giza, Egypt2Fakultat Chemie und Lebensmittelchemie, TU-Dresden, Dresden, Germany3Chemistry Department, Faculty ofScience, Islamic University in AlmadinahAlmonawara, Almadinah Almonawara,Saudi Arabia4Chemistry Department, Faculty ofScience, Bani Suef University, Bani Suef,Egypt5Science & Technology Center ofExcellence, Ministry of MilitaryProduction, Cairo, Egypt

CorrespondenceSobhi M. Gomha, Chemistry Department,Faculty of Science, Cairo University, Giza12613, Egypt.Email: s.m.gomha@gmail.com

Abstract

A novel series of 1,5-dihydropyrido-triazolo-pyrimidine derivatives were pre-

pared by cyclocondensation of 2-thioxo-pyrido[2,3-d]pyrimidines (prepared

from reaction of chalcone with 6-aminothiouracil) with a variety of

hydrazonoyl chlorides. Based on spectroscopic evidence and their chemical

syntheses, the structures of the newly prepared compounds were elucidated.

Designated compounds are forced for molecular docking by using MOE

2014.010 Package software; one of in silico study tools. Synthesized compounds

are targeting Human Cyclin-defendant Kinase 2 (CK2) PDB ID (1PXO.Protein

data bank) due to its important role in controlling the human cell cycle and

also for meiosis.

1 | INTRODUCTION

In continuation of our studies dealing with the utility ofhydrazonoyl halides for synthesis of various bridgeheadnitrogen polyheterocycles,[1–5] substituted pyrido[2,3-d]pyrimidines have a broad variety of physiological charac-teristics, including anti-inflammatory, analgesic,[6]

antibacterial,[7] antitumoral,[8] and antileishmanialagents.[9] They also act as dihydrofolate reductase inhibi-tors and tyrosine kinase inhibitors.[10] Some drugs,including antiasthmatic pemirolast,[11] tranquilizingpirenperoazne,[12] antiulcerative agents,[13] antiallergicBarmastine,[14] also have the pyrido[1,2-a]pyrimidineskeleton. Therefore, the synthesis of such ring systemshas been very interesting in view of their potent biologi-cal and pharmacological activities.[15–23] The tricyclicpyrido[2,3-d][1,2,4]triazolo [4,3-a]pyrimidin-5-ones arepharmacological scaffold that represent a wide range ofbiological activities.[24–28] Cyclin-dependent kinases

(CDKs) are serine/threonine kinases that control the pro-liferation of eukaryotic cells. Due to their crucial role inthe regulation of the cell division cycle, CDKs haveemerged as important therapeutic targets in anticancerdrug research. Azolopyrimidine derivatives such astriazolo-pyrimidines, pyrazolo-pyrimidines and pyrrolo-pyrimidines were shown to potently inhibit cyclin-dependent kinase 2 (CDK2) (Figure 1).[29–31]

In these last two decades, we have launched a pro-gram designed to create new easy, synthetic paths to het-erocyclic systems that are functionally replaced, usinginexpensive laboratory materials with anticipatedbioactivities.[32–42] Under our program, some newpyridine-fused aza heterocyclic compounds have to beevaluated for biological activity. It was expected thatcombining a triazole ring with a pyridine and/or a pyrim-idine ring in one system could lead to improved biologi-cal activity. Thus, we targeted pyrido-triazolo-pyrimidinederivatives bearing an ethoxy-carbonyl group.

Received: 6 September 2019 Revised: 16 December 2019 Accepted: 30 December 2019

DOI: 10.1002/jhet.3901

J Heterocyclic Chem. 2020;57:1759–1769. wileyonlinelibrary.com/journal/jhet © 2020 Wiley Periodicals, Inc. 1759

Functionally substituted chalcones derived from ethylacetoacetate 1 seemed suitable starting materials to fulfillthis objective. To prevent the active methylene of 1 frominterfering in the condensation reaction, it was manda-tory to block it through coupling with diazonium salts.

2 | RESULTS AND DISCUSSION

Ethyl acetoacetate 1 was coupled with two substitutedbenzene diazonium chlorides to give the aryl hydrazones2a,b. These latter compounds were allowed to condensewith benzaldehyde and sodium hydroxide to give thechalcones 3a,b, respectively (Scheme 1).

The pyrido[2,3-d]pyrimidine derivatives 8a,b wereprepared from reaction of chalcones 3a,b with the6-aminothiouracil 4, rather than their position isomers10a,b, which would have been readily cyclized into thetriazaphenalene derivatives 11a,b (Scheme 2). The reac-tion presumably occurs according to the procedurereported by Quiroga et al[43] via the condensation of theamino group of 4 with the carbonyl group of 3a,b toafford the intermediates 5a,b that in situ undergoelectrocyclization to afford the intermediates 6a,b or their

tautomers 7a,b, which in role undergo an autooxidationto afford the final isolable pyrido[2,3-d]pyrimidine prod-ucts 8a,b, respectively. The presence of the ester tripletand quartet signals in the 1H NMR spectra of 8a and 8bas well as the MS and the elemental analyses confirmedtheir structures.

Compounds 8a,b have been reacted with varioushydrazonoyl chlorides 12 to give the pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives 15a-q. The reactionis presumed to continue through S-alkylation withremoval of HCl to afford intermediates 13 that undergoSmiles rearrangement to afford the thiohydrazide inter-mediates 14 that lose H2S to afford the final products(Scheme 3).

3 | MOLECULAR DOCKING

Designated compounds are forced for molecular dockingby using MOE2014.010 Package software one of in silicostudy tools. The synthesized compounds are targetingHuman Cyclin-defendant Kinase 2 (CK2) PDB ID (1PXO.Protein data bank) due to its important role in controllingof the human cell cycle and also for meiosis.

Synthesized compounds prepared for modeling byadding hydrogen and forced to energy minimization alsotargeted protein prepared for docking by protein optimi-zation process and minimization of energy in order tomeet all the residues involved in the active protein site.

All four synthesized compounds and the protein'snative inhibitor (4-(2-amino-4-methyl-thiazol-5-yl)-pyrimidin-2-yl]-(3-nitro-phenyl)-amine) reveal variousbinding energies. Compound 15a showing total bindingenergies (−12.5) Kcal/mol by making three pi-hydrogeninteraction with Ile 10 with binding energies (−1.1, −1.0)Kcal/mol, with Gly 13 with binding energy (−0.7) Kcal/

N

N N

N

NH

HO

HN

Roscovitine

N

N N

N

HN

N

OH

O

Dinaciclib

N N

N

OPh

EtOOC

NHN

Ar

NN

Ar`

R

Targetpyridotriazolopyrimidines

15a,e,fand15l

N

N NH

N

NH

O

H2NO2S

NU6102

N

N

N

N

HN

O

SO2NH2

N

N

N

N

HN

N

Br

TriazolopyrimidinesshowedgoodactivitytowardsCDK2

FIGURE 1 Different examples of CDK2 and target

compounds 15 [Color figure can be viewed at

wileyonlinelibrary.com]

SCHEME 1 Synthesis of chalcone derivatives 3a,b

1760 ABDELRAZEK ET AL.

mol, Hydrogen donor interaction with Glu 162 with bind-ing energy −7.6 Kcal/mol and hydrogen acceptor interac-tion with Glu 12 with binding energy −2.1 Kcal/mo(Figure 2).

On the other side, compound 15e shows strong affin-ity to the (ck2) enzyme with a total binding energy equalto −13.6 Kcal/mol by expressing to pi-hydrogen interac-tions with Ile 10 with binding energies (−0.9, −0.9) Kcal/

3a,b

4

7a,b

NH

NH

S

O

H2N

N NH

NH

S

OPh

EtOOC

NHN

Ar

AcOH

EtO

OO

NHN

Ar

Ph

Ar = a, Ph; i, 3,5-(Me)2C6H3

Ar = a, Ph; b, 3,5-(Me)2C6H3

Auto-oxidation

N NH

NH

S

OPh

EtOOC

NHN

Ar

H

NH

NH

NH

S

OPh

EtOOC

NHN

Ar

N NH

NH

S

OPh

EtOOC

NHN

Ar

6a,b

5a,b

8a,b

EtO

OO

NHN

Ar

Ph

NH

NH

S

O

HN

N NH

NH

S

O

Ph

COOEtN

NHAr

9a,b 10a,b

N NH

N

S

O

Ph

N

NHAr

O

11a,b

SCHEME 2 Synthesis of 2-thioxo-

pyrido[2,3-d]pyrimidines 8a,b

SCHEME 3 Synthesis of

1,5-dihydropyrido-triazolo-pyrimidine

derivatives (15a-q)

ABDELRAZEK ET AL. 1761

mol, hydrogen donor interaction with Glu 162 with −9.7Kcal/mol binding energy, and hydrogen acceptor interac-tion with −2.1 Kcal/mol binding energy with Glu12 (Figure 3).

While total binding energies of compound 15f reveal-ing a weak affinity to the (ck2) enzyme giving −0.9 Kcal/mol by making pi-hydrogen interaction with Val18 (Figure 4).

Finally the potency of compound 15l as inhibitorto the (ck2) enzyme was explained by the total

binding energies which equal −13.1 Kcal/mol. Com-pound 15l makes two pi-hydrogen interactions withIle 10 with binding energies (−1.0, −1.0) Kcal/mol,hydrogen donor interaction with Glu 162 with −9.7Kcal/mol binding energy, and hydrogen acceptorinteraction with Glu12 with −1.4 Kcal/mol bindingenergy (Figure 5).

From the above studies, compound 15f revealing thelowest affinity to the (ck2) enzyme compared to the threeothers compounds (15a, 15e, and 15f) (Figure 6), which

FIGURE 2 Compund 15a fitted into the

active binding site of (ck2) enzyme [Color figure

can be viewed at wileyonlinelibrary.com]

FIGURE 3 Compund 15e fitted into the

active binding site of (ck2) enzyme [Color figure

can be viewed at wileyonlinelibrary.com]

1762 ABDELRAZEK ET AL.

emphasize the position of substituents (pharmacophores)affecting strongly on the potency of the candidate drugby affecting the fitting of the drug into the active bindingsite of the targeted enzyme.

4 | EXPERIMENTAL

Electrothermal IA-9000 apparatus was used for recordingall melting points of new derivatives. After preparation of

FIGURE 4 Compund 15f fitted into the

active binding site of (ck2) enzyme [Color figure

can be viewed at wileyonlinelibrary.com]

FIGURE 5 Compund 15l fitted into the

active binding site of (ck2) enzyme [Color figure

can be viewed at wileyonlinelibrary.com]

ABDELRAZEK ET AL. 1763

KBr discs of the new synthesized fused cycloheptane deriva-tives, IR-spectra were determined using Raman spectrome-ter (Nexus 670 FT-IRFT). NMR spectra were acquired on aBruker Avance 400 instrument at 400 MHz for 1H NMR inDMSO-d6 solutions, using residual solvent signals as inter-nal standards. Also, measuring of elemental analyzes werecarried out on Elementar vario-LIII C-H-N-S analyzer. Themass spectra were measured on MS Spectrometer (GCMS-QP 1000EX Shimadzu Gas Chromatography). TLC usingaluminum sheets were utilized to monitor the progress andpurity of the products, and all spots were disclosed byexposure to UV lamp. Ethyl 3-oxo-2-(2-phenylhydrazono)-butanoate derivatives 2a and 2b[44] and 6-amino-2-thioxo-2,-3-dihydropyrimidin-4(1H)-one[45] hydrazonoyl chlorides12a-k[46] were prepared as described in the literature.

4.1 | Synthesis of chalcones 3a and 3b

To an ethanolic solution of each of ethyl 3-oxo-2-(2-phenylhydrazono)-butanoate derivatives 2a or 2b(10 mmol) and benzaldehyde (1.06 g, 10 mmol), an aqueoussodium hydroxide solution (50%, 10 mL) was slowly addedwith stirring at 25�C for 4 to 6 hours as indicated by TLC.The reaction mixture was poured into ice-cold water, andthe product that separated was filtered, dried, and crystal-lized from ethanol to give chalcones 5a-d, respectively.

4.2 | Ethyl 3-oxo-5-phenyl-2-(2-phenylhydrazono)pent-4-enoate (3a)

Yellow solid (2.6 g; 82% yield), mp 200�C to 202�C(EtOH); νmax = 3462 (NH), 3069, 2929 (CH), 1729, 1654

(2C=O), 1603 (C=N) cm−1; δH = 1.21 (t, J = 7.3 Hz, 3H,CH3), 4.15 (q, J = 7.3 Hz, 2H, CH2), 6.84 (d, J = 15.8 Hz,1H, CH=CH), 6.87 to 7.51 (m, 10H, Ar-H), 7.88 (d,J = 15.8 Hz, 1H, CH=CH), 11.42 (s, 1H, NH) ppm; MS,m/z (%) 322 (M+, 29). Anal. Calcd. For C19H18N2O3

(322.36): C, 70.79; H, 5.63; N, 8.69. Found: C, 70.68; H,5.60; N, 8.49%.

4.3 | Ethyl 2-(2-[3,5-dimethylphenyl]hydrazono)-3-oxo-5-phenylpent-4-enoate (3b)

Yellow solid (2.76 g; 79% yield), mp168�C to 188�C(EtOH); νmax = 3421 (NH), 3024, 2918 (CH), 1729, 1692(2C=O), 1613 (C=N) cm−1; δH = 1.23 (t, J = 7.3 Hz,3H, CH3), 2.25 (s, 3H, CH3), 2.36 (s, 3H, CH3), 4.22 (q,J = 7.3 Hz, 2H, CH2), 6.24 (d, J = 15.8 Hz, 1H,CH=CH), 6.54 to 7.24 (m, 8H, Ar-H), 7.27 (d,J = 15.8 Hz, 1H, CH=CH), 11.50 (s, 1H, NH) ppm; MS,m/z (%) 350 (M+, 27). Anal. Calcd. For C21H22N2O3

(350.41): C, 71.98; H, 6.33; N, 7.99. Found: C, 71.78; H,6.12; N, 7.80%.

4.4 | Synthesis of ethyl 2-(4-oxo-5-aryl-2-thioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidin-7-yl)-2-(2-phenylhydrazono)acetates 8a,b

Chalcones 2a or 2b (10 mmol) were refluxed for 12 hourswith 6-aminothiouracil 4 (1.43 g, 10 mmol) in 30 mL ofAcOH. The obtained product after evaporation was fil-tered and recrystallized from dioxane to give the respec-tive thiones 8a,b.

4.5 | Ethyl 2-(2-phenylhydrazono)-2-(1,2,3,4-tetrahydro-4-oxo-5-phenyl-2-thioxopyrido[2,3 d]pyrimidin-7-yl)acetate (8a)

Brown solid (3.34 g; 75% yield), mp 239�C to 241�C (diox-ane); νmax = 3423 to 3320 (3NH), 3043, 2921 (CH), 1726,1650 (2C=O), 1605 (C=N) cm−1; δH = 1.21 (t, 3H, CH3),4.27 (q, 2H, CH2), 6.35 (s, 1H, NH), 6.85 to 8.04 (m, 11H,Ar-H), 11.27, 11.59 (2s, 2H, 2NH) ppm; 13C NMR(DMSO-d6): δ 14.44 (CH3), 62.73 (CH2), 114.58, 115.58,123.48, 127.06, 128.05, 128.59, 130.40, 132.48, 133.39,139.06, 139.16, 142.95, 143.10, 150.76, 159.81(Ar–C andC=N), 165.03 (C=O), 178.39 (C=S) ppm; MS, m/z (%)445 (M+, 54). Anal. Calcd. For C23H19N5O3S (445.49): C,62.01; H, 4.30; N, 15.72. Found: C, 61.90; H,4.18; N, 15.60%.

FIGURE 6 Graph showing the different binding energies of

the four compounds and the native inhibitor (Nat.Inh) [Color

figure can be viewed at wileyonlinelibrary.com]

1764 ABDELRAZEK ET AL.

4.6 | Ethyl 2-(2-[3,5-dimethylphenyl]hydrazono)-2-(1,2,3,4-tetrahydro-4-oxo-5-phenyl-2-thioxopyrido[2,3-d]pyrimidin-7-yl)acetate (8b)

Brown solid (3.78 g; 80% yield), mp 220�C to 222�C (diox-ane); νmax = 3423 to 3320 (3NH), 3043, 2921 (CH), 1726,1650 (2C=O), 1605 (C=N) cm−1; δH = 1.22 (t, 3H, CH3),2.25 (s, 3H, CH3), 2.36 (s, 3H, CH3), 4.22 (q, 2H, CH2),6.38 (s, 1H, NH), 6.53 to 7.50 (m, 8H, Ar–H), 7.58 (s, 1H,pyridine 5-H), 11.20 & 11.48 (2s, 2H, 2NH); MS, m/z (%)473 (M+, 54). Anal. Calcd. For C25H23N5O3S (473.55): C,63.41; H, 4.90; N, 14.79. Found C, 63.33; H,4.75; N, 14.67%.

4.7 | Synthesis of 1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate derivatives (15a-q)

4.7.1 | General procedure

Triethylamine (1 mL, 10 mmol) has been added to amixture of thione 8a or 8b (10 mmol) andhydrazonoyl halides 12a-k (10 mmol) in 10 mL diox-ane. The reaction mixture was refluxed for 5 to10 hours. Evaporate solvent, filter the formed solid,washed with methanol, dried, and recrystallized fromthe proper solvent to give the products 15a-q, respec-tively. Compounds 15a-q and their analytical con-stants are listed below.

4.8 | Ethyl 2-(3-acetyl-5-oxo-1,6-diphenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-phenylhydrazono)acetate (15a)

Brown solid (4.45 g; 78% yield), mp 175�C to 177�C (diox-ane); νmax = 3377 (NH), 3059, 2922 (CH), 1726, 1693,1667 (3C=O), 1598 (C=N) cm−1; δH = 1.27 (t, 3H, CH3),2.38 (s, 3H, CH3), 4.27 (q, 2H, CH2), 7.09 to 8.10 (m, 15H,Ar–H), 8.46 (s, 1H, pyridine-H7), 11.90 (s, 1H, NH) ppm;13C NMR (DMSO-d6): δ 12.07, 24.06 (CH3), 61.43 (CH2),111.52, 112.06, 114.34, 114.52, 116.22, 123.76, 124.11,125.82, 127.91, 128.28, 129.38, 129.59, 136.30, 137.13,141.47, 142.69, 143.38, 146.28, 156.13, 156.62 (Ar–C andC=N), 162.85, 175.91, 195.57(C=O) ppm; MS, m/z (%)571 (M+, 31). Anal. Calcd. For C32H25N7O4 (571.59): C,

67.24; H, 4.41; N, 17.15. Found: C, 67.15; H,4.33; N, 17.06%.

4.9 | Ethyl 2-(3-acetyl-5-oxo-6-phenyl-1-[p-tolyl]-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-phenylhydrazono)acetate (15b)

Brown solid (4.45 g; 76% yield), mp 185�C to 187�C (diox-ane); νmax = 3375 (NH), 3090, 2923 (CH), 1729, 1689,1662 (3C=O), 1594 (C=N) cm−1; δH = 1.27 (t, 3H, CH3),2.27 (s, 3H, CH3), 2.34 (s, 3H, CH3), 4.31 (q, 2H, CH2),7.16 to 7.98 (m, 14H, Ar–H), 8.40 (s, 1H, pyridine-H7),11.53 (s, 1H, NH) ppm; MS, m/z (%) 585 (M+, 60). Anal.Calcd. For C33H27N7O4 (585.61): C, 67.68; H, 4.65; N,16.74. Found: C, 67.55; H, 4.46; N, 16.80%.

4.10 | Ethyl 2-(3-acetyl-1-[4-chlorophenyl]-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-phenylhydrazono)acetate (15c)

Brown solid (4.48 g; 74% yield), mp 190�C to 192�C (diox-ane); νmax = 3405 (NH), 3040, 2921 (CH), 1729, 1710,1660 (3C=O), 1597 (C=N) cm−1; δH = 1.27 (t, 3H, CH3),2.38 (s, 3H, CH3), 4.25 (q, 2H, CH2), 7.18 to 8.08 (m, 14H,Ar–H), 8.43 (s, 1H, pyridine-H7), 11.58 (s, 1H, NH) ppm;MS, m/z (%) 605 & 607 (M−1 & M+1, 60). Anal. Calcd. forC32H24ClN7O4 (606.03): C, 63.42; H, 3.99; N, 16.18.Found: C, 63.31; H, 3.82; N, 16.08%.

4.11 | Ethyl 2-(3-acetyl-1-(3-chlorophenyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-phenylhydrazono)acetate (15d)

Brown solid, (4.79 g; 79% yield); mp 200�C to 202�C(dioxane); νmax = 3388 (NH), 3065, 2923 (CH), 1725,1684, 1663 (3C=O), 1591 (C=N) cm−1; δH = 1.27 (t, 3H,CH3), 2.37 (s, 3H, CH3), 4.23 (q, 2H, CH2), 7.09 to 8.13(m, 14H, Ar-H), 8.40 (s, 1H, pyridine-H7), 11.55 (s, 1H,NH) ppm; MS m/z (%): 605 & 607 (M−1 & M+1, 15). Anal.Calcd. for C32H24ClN7O4 (606.03): C, 63.42; H, 3.99; N,16.18. Found: C, 63.33; H, 3.85; N, 16.02%.

ABDELRAZEK ET AL. 1765

4.12 | Ethyl 2-(3-acetyl-1-(4-bromophenyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-phenylhydrazono)acetate (15e)

Brown solid, (5.2 g; 80% yield); mp 205�C to 207�C (diox-ane); νmax = 3397 (NH), 3048, 2922 (CH), 1723, 1679,1662 (3C=O), 1596 (C=N) cm−1; δH = 1.26 (t, 3H, CH3),2.38 (s, 3H, CH3), 4.19 (q, 2H, CH2), 7.19 to 7.97 (m, 14H,Ar-H), 8.39 (s, 1H, pyridine-H7), 11.57 (s, 1H, NH) ppm;MS m/z (%): 649 & 651 (M−1 & M+1, 13). Anal. Calcd. forC32H24BrN7O4 (650.48): C, 59.09; H, 3.72; N, 15.07.Found: C, 58.95; H, 3.66; N, 14.92%.

4.13 | Ethyl 8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-5-oxo-1,6-diphenyl-1,5-dihydropyrido [2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15f)

Brown solid (4.75 g; 79% yield); mp 170�C to 172�C (diox-ane); νmax = 3386 (NH), 3050, 2916 (CH), 1748, 1724,1660 (3C=O), 1586 (C=N) cm−1; δH = 1.21 (t, 3H, CH3),1.27 (t, 3H, CH3), 4.35 (q, 2H, CH2), 4.38 (q, 2H, CH2),7.02 to 8.08 (m, 15H, Ar-H), 8.28 (s, 1H, pyridine-H7),11.24 (s, 1H, NH) ppm; 13C-NMR (DMSO-d6): δ 13.16,13.67 (CH3), 62.38, 62.73 (CH2), 101.29, 111.59, 111.74,114.63, 116.22, 125.52, 126.53, 127.66, 130.26, 136.42,138.30, 138.58, 139.80, 139.89, 142.36, 146.18, 150.26,156.42, 158.36, 159.89, (Ar–C and C=N), 165.68, 167.66,175.60 (C=O) ppm; MS m/z (%): 601 (M+, 19). Anal.Calcd. for C33H27N7O5 (601.61): C, 65.88; H, 4.52; N,16.30. Found: C, 65.78; H, 4.45; N, 16.21%.

4.14 | Ethyl 8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-5-oxo-6-phenyl-1-(p-tolyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15g)

Brown solid, (4.5 g; 74% yield); mp 140�C to 142�C (diox-ane); νmax = 3388 (NH), 3069, 2922 (CH), 1744, 1722,1673 (3C=O), 1591 (C=N) cm−1; δH = 1.27 (t, 3H, CH3),1.38 (t, 3H, CH3), 2.32 (s, 3H, CH3), 4.35 (q, 2H, CH2),4.37 (q, 2H, CH2), 7.13 to 7.97 (m, 14H, Ar–H), 8.31 (s,1H, pyridine-H7), 11.22 (s, 1H, NH) ppm; MS m/z (%):615 (M+, 32). Anal. Calcd. for C34H29N7O5 (615.64): C,

66.33; H, 4.75; N, 15.93. Found: C, 66.38; H,4.72; N, 15.80%.

4.15 | Ethyl 8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-5-oxo-6-phenyl-1-(m-tolyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15h)

Brown solid (4.6 g; 75% yield); mp 163�C to 165�C (diox-ane); νmax = 3384 (NH), 3059, 2923 (CH), 1748, 1724,1675 (3C=O), 1594 (C=N) cm−1; δH = 1.25 (t, 3H, CH3),1.27 (t, 3H, CH3), 2.38 (s, 3H, CH3), 4.38 (q, 2H, CH2),4.41 (q, 2H, CH2), 7.19 to 7.98 (m, 14H, Ar–H), 8.28 (s,1H, pyridine-H7), 11.22 (s, 1H, NH) ppm; MS m/z (%):615 (M+, 20). Anal. Calcd. for C34H29N7O5 (615.64): C,66.33; H, 4.75; N, 15.93. Found: C, 66.21; H,4.65; N, 15.87%.

4.16 | Ethyl 1-(4-chlorophenyl)-8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15i)

Brown solid (4.77 g; 75% yield); mp 155�C to 157�C (diox-ane); νmax = 3392 (NH), 3061, 2927 (CH), 1748, 1725,1678 (3C=O), 1598 (C=N) cm−1; δH = 1.27 (t, 3H, CH3),1.37 (t, 3H, CH3), 4.35 (q, 2H, CH2), 4.38 (q, 2H, CH2),7.22 to 8.09 (m, 14H, Ar–H), 8.34 (s, 1H, pyridine-H7),11.32 (s, 1H, NH) ppm; MS m/z (%): 635 & 637 (M−1 &M+1, 13). Anal. Calcd. for C33H26ClN7O5 (636.06): C,62.31; H, 4.12; N, 15.41. Found C, 62.22; H,4.01; N, 15.33%.

4.17 | Ethyl 8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-1-(4-nitrophenyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15j)

Brown solid (4.7 g; 73% yield); mp 165�C to 167�C (diox-ane); νmax = 3403 (NH), 3055, 2923 (CH), 1749, 1729,1680 (3C=O), 1592 (C=N) cm−1; δH = 1.25 (t, 3H, CH3),1.40 (t, 3H, CH3), 4.35 (q, 2H, CH2), 4.39 (q, 2H, CH2),7.19 to 8.16 (m, 14H, Ar-H), 8.38 (s, 1H, pyridine-H7),11.55 (s, 1H, NH) ppm; MS m/z (%): 646 (M+, 61). Anal.

1766 ABDELRAZEK ET AL.

Calcd. for C33H26N8O7 (646.61): C, 61.30; H, 4.05; N,17.33. Found C, 61.21; H, 3.92; N, 17.21%.

4.18 | Ethyl 1-(2,4-dichlorophenyl)-8-(2-ethoxy-2-oxo-1-(2-phenylhydrazono)ethyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15k)

Brown solid (4.6 g; 69% yield); mp 155�C to 157�C (diox-ane); νmax = 3398 (NH), 3045, 2928 (CH), 1749, 1724,1650 (3C=O), 1591 (C=N) cm−1; δH = 1.18 (t, 3H, CH3),1.22 (t, 3H, CH3), 4.26 (q, 2H, CH2), 4.29 (q, 2H, CH2),7.05 to 7.98 (m, 13H, Ar–H), 8.25 (s, 1H, pyridine-H7),11.36 (s, 1H, NH) ppm; MS m/z (%): 669 & 671 (M−1 &M+1, 46). Anal. Calcd. for C33H25Cl2N7O5 (670.5): C,59.11; H, 3.76; N, 14.62. Found C, 59.00; H,3.66; N, 14.55%.

4.19 | Ethyl 2-(3-acetyl-5-oxo-1,6-diphenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-[3,5-dimethylphenyl]hydrazono)acetate (15l)

Brown solid (4.7 g; 79% yield); mp 184�C to 186�C (diox-ane); νmax = 3308 (NH), 3024, 2919 (CH), 1720, 1673,1665 (3C=O), 1588 (C=N) cm−1; δH = 1.24 (t, 3H, CH3),2.28 (s, 3H, CH3), 2.36 (s, 3H, CH3), 2.41 (s, 3H, CH3),4.27 (q, 2H, CH2), 7.06 to 7.65 (m, 13H, Ar–H), 8.10 (s,1H, pyridine-H7), 11.55 (s, 1H, NH) ppm; MS m/z (%):599 (M+, 21). Anal. Calcd. for C34H29N7O4 (599.64): C,68.10; H, 4.87; N, 16.35;. Found C, 67.97; H,4.78; N, 16.22%.

4.20 | Ethyl 2-(3-acetyl-5-oxo-6-phenyl-1-(p-tolyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-[3,5-dimethylphenyl]hydrazono)acetate (15m)

Brown solid (4.17 g; 68% yield); mp 185�C to 187�C (diox-ane); νmax = 3330 (NH), 3050, 2918 (CH), 1718, 1671,1664 (3C=O), 1588 (C=N) cm−1; δH = 1.23 (t, 3H, CH3),2.27 (s, 3H, CH3), 2.30 (s, 3H, CH3), 2.35 (s, 3H, CH3),2.40 (s, 3H, CH3), 4.25 (q, 2H, CH2), 6.94 to 7.58 (m, 12H,Ar-H), 8.17 (s, 1H, Pyridine-H7), 11.52 (s, 1H, NH) ppm;MS m/z (%): 613 (M+, 20). Anal. Calcd. for C35H31N7O4

(613.67): C, 68.50; H, 5.09; N, 15.98. Found C, 68.39; H,4.98; N, 15.89%.

4.21 | Ethyl 2-(3-acetyl-1-(4-chlorophenyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-8-yl)-2-(2-[3,5-dimethylphenyl]hydrazono)acetate (15n)

Brown solid (4.37 g; 69% yield); mp 250�C to 252�C (diox-ane); νmax = 3374 (NH), 3060, 2919 (CH), 1726, 1685,1669 (3C=O), 1589 (C=N) cm−1; δH = 1.25 (t, 3H, CH3),2.28 (s, 3H, CH3), 2.30 (s, 3H, CH3), 2.36 (s, 3H, CH3),4.15 (q, 2H, CH2), 6.85 to 7.65 (m, 12H, Ar–H), 8.19 (s,1H, pyridine-H7), 11.58 (s, 1H, NH) ppm; MS m/z (%):633 & 635 (M−1 & M+1, 16). Anal. Calcd. forC34H28ClN7O4 (634.08): C, 64.40; H, 4.45;N, 15.46.Found C, 64.39; H, 4.34;N, 15.36%.

4.22 | Ethyl 8-(1-(2-[3,5-dimethylphenyl]hydrazono)-2-ethoxy-2-oxoethyl)-5-oxo-1,6-diphenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15o)

Brown solid (4.5 g; 72% yield); mp 125�C to 127�C (diox-ane); νmax = 3417 (NH), 3058, 2920 (CH), 1741, 1719, 1651(3C=O), 1605 (C=N) cm−1; δH = 1.26 (t, 3H, CH3), 1.39 (t,3H, CH3), 2.26 (s, 3H, CH3), 2.32 (s, 3H, CH3), 4.28 (q, 2H,CH2), 4.32 (q, 2H, CH2), 6.67 to 7.59 (m, 13H, Ar–H), 8.38(s, 1H, pyridine-H7), 11.24 (s, 1H, NH) ppm; MS m/z (%):629 (M+, 38). Anal. Calcd. for C35H31N7O5 (629.66): C,66.76; H, 4.96; N, 15.57. Found C, 66.67; H, 4.82; N, 15.45%.

4.23 | Ethyl 8-(1-(2-[3,5-dimethylphenyl]hydrazono)-2-ethoxy-2-oxoethyl)-5-oxo-6-phenyl-1-(p-tolyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15p)

Brown solid (4.95 g; 77% yield); mp 195�C to 197�C (diox-ane); νmax = 3396 (NH), 3043, 2920 (CH), 1743, 1719,1653 (3C=O), 1602 (C=N) cm−1; δH = 1.26 (t, 3H, CH3),1.31 (t, 3H, CH3), 2.26 (s, 3H, CH3), 2.31 (s, 3H, CH3),2.36 (s, 3H, CH3), 4.28 (q, 2H, CH2), 4.40 (q, 2H, CH2),6.67 to 7.58 (m, 12H, Ar-H), 8.35 (s, 1H, pyridine-H7),11.55 (s, 1H, NH) ppm; MS m/z (%): 643 (M+, 19). Anal.

ABDELRAZEK ET AL. 1767

Calcd. for C36H33N7O5 (643.69): C, 67.17; H, 5.17; N,15.23. Found C, 67.03; H, 5.05; N, 15.12%.

4.24 | Ethyl 1-(4-chlorophenyl)-8-(1-(2-[3,5-dimethylphenyl]hydrazono)-2-ethoxy-2-oxoethyl)-5-oxo-6-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (15q)

Brown solid (4.9 g; 74% yield); mp 160�C to 162�C (diox-ane); νmax = 3242 (NH), 3025, 2920 (CH), 1745, 1725, 1651(3C=O), 1603 (C=N) cm−1; δH = 1.26 (t, 3H, CH3), 1.39 (t,3H, CH3), 2.26 (s, 3H, CH3), 2.31 (s, 3H, CH3), 4.27 (q, 2H,CH2), 4.35 (q, 2H, CH2), 6.67 to 7.59 (m, 12H, Ar-H), 8.42(s, 1H, pyridine-H7), 11.31 (s, 1H, NH) ppm; MS m/z (%):664 (M+, 19). Anal. Calcd. for C35H30ClN7O5 (664.11): C,63.30; H, 4.55; N, 14.76. Found C, 63.21; H, 4.43; N, 14.70%.

5 | CONCLUSION

During the current investigation, we synthesized numer-ous diversely substituted 1,5-dihydropyrido-triazolo-pyrimidine derivatives from cheap laboratory accessiblestarting materials. Since a variety of 1,5-dihydropyrido-triazolo-pyrimidine derivatives 15a-q were synthesizedfrom reaction of 2-thioxo-pyrido[2,3-d]pyrimidine deriva-tives 8a,b with a variety of hydrazonoyl chlorides 12. Theproduct structures were elucidated based on their analyti-cal and spectral data. Designated compounds are forcedfor molecular docking by using MOE 2014.010 Packagesoftware. Synthesized compounds are targeting HumanCyclin-defendant Kinase 2 (CK2) PDB ID (1PXO.Proteindata bank) due to its important role in controlling of thehuman cell cycle and also for meiosis.

ACKNOWLEDGMENTSWe are grateful to the Alexander von Humboldt Founda-tion (Germany) for the continued support toF.M.A. through granting short research fellowships; thelast one (June–August 2018); during this time, a consider-able part of the analyses and spectra of this work hasbeen carried out.

CONFLICT OF INTERESTThe authors declare no conflicts of interest.

ORCIDFathy M. Abdelrazek https://orcid.org/0000-0003-1179-649XSobhi M. Gomha https://orcid.org/0000-0002-7739-2837

Hassan M. Abdel-aziz https://orcid.org/0000-0002-3440-2927

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SUPPORTING INFORMATIONAdditional supporting information may be found onlinein the Supporting Information section at the end of thisarticle.

How to cite this article: Abdelrazek FM,Gomha SM, Abdel-aziz HM, Farghaly MS, Metz P,Abdel-Shafy A. Efficient synthesis and In Silicostudy of some novel pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives. J Heterocyclic Chem.2020;57:1759–1769. https://doi.org/10.1002/jhet.3901

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