Synthesis of some novel annulated pyrido[2,3-d]pyrimidines via stereoselective intramolecular hetero Diels–Alder reactions of 1-oxa-1,3-butadienes

• Mohit L. Deb and
• Pulak J. Bhuyan

Beilstein J. Org. Chem. 2010, 6, No. 11, doi:10.3762/bjoc.6.11

• Mohit L. Deb Pulak J. Bhuyan Medicinal Chemistry Division, North East Institute of Science & Technology, Jorhat 785006, Assam, India, Fax: 0376 2370011 10.3762/bjoc.6.11 Abstract Some novel annulated pyrido[2,3-d]pyrimidines 6 and 7 were synthesized stereoselectively by intramolecular hetero

• Diels–Alder reactions involving 1-oxa-1,3-butadienes. Keywords: β-halo aldehydes; hetero Diels–Alder reaction; 1-oxa-1,3-butadiene; pyrido[2,3-d]pyrimidines; uracil; Introduction The importance of uracil and its annulated derivatives is well recognized by synthetic as well as biological chemists [1][2

• ][3][4][5][6][7][8]. Pyrido[2,3-d]pyrimidines represent a broad class of annelated uracils which have received considerable attention over the past years due to their wide range of biological activities such as antibacterial [9][10], antitumor [11][12], cardiotonic [13][14], hepatoprotective [13

Synthesis of 2-substituted 9-oxa-guanines {5-aminooxazolo[5,4-d]pyrimidin- 7(6H)-ones} and 9-oxa-2-thio- xanthines {5-mercaptooxazolo[5,4-d]pyrimidin- 7(6H)-ones}

• Subrata Mandal,
• Wen Tai Li,
• Yan Bai,
• Jon D. Robertus and
• Sean M. Kerwin

Beilstein J. Org. Chem. 2008, 4, No. 26, doi:10.3762/bjoc.4.26

• Subrata Mandal Wen Tai Li Yan Bai Jon D. Robertus Sean M. Kerwin College of Pharmacy, 1 University Station, University of Texas, Austin, TX, 78712, USA Department of Biochemistry,1 University Station, University of Texas, Austin, TX, 78712, USA 10.3762/bjoc.4.26 Abstract Oxazolo[5,4-d]pyrimidines

• preparation of a series of 2-substituted 5-aminooxazolo[5,4-d]pyrimidin-7(6H)-ones and related 5-thio-oxazolo[5,4-d]pyrimidines is described, including analogs suitable for further elaboration employing “click” chemistry utilizing copper-catalyzed Huisgen 1,3-dipolar cycloadditions. Two of the compounds

• prepared were found to inhibit ricin with IC50 ca. 1–3 mM. Keywords: Annulation; Click Chemistry; Cyclization; Purine Analogs; Ricin; Introduction Oxazolo[5,4-d]pyrimidines have been reported to possess a variety of biological activities including kinase inhibition [1][2], adenosine receptor antagonism

Perhalogenated pyrimidine scaffolds. Reactions of 5-chloro- 2,4,6-trifluoropyrimidine with nitrogen centred nucleophiles

• Emma L. Parks,
• Graham Sandford,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2008, 4, No. 22, doi:10.3762/bjoc.4.22

• desirable process but one of the most difficult to achieve in practice. Pyrimidines are electron-deficient aromatic systems and, when halogenated, become very useful substrates for a variety of nucleophilic aromatic substitution (SNAr) processes [9] and, since numerous chloropyrimidines are commercially

The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

• Dipak Prajapati and
• Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

• undergoing a 1,5-(4 → 5) hydride shift prior to cyclization to yield a 6-membered ring product 6 (Scheme 2). This is in contrast to an earlier report by Sandhu et al to obtain pyrrolo [2,3-d]pyrimidines from 6-tert-amino-substituted uracils and dimethyl acetylenedicarboxylate.[32] However, further work is in

An easy synthesis of 5-functionally substituted ethyl 4-amino- 1-aryl- pyrazolo- 3-carboxylates: interesting precursors to sildenafil analogues

• Said A. S. Ghozlan,
• Khadija O. Badahdah and
• Ismail A. Abdelhamid

Beilstein J. Org. Chem. 2007, 3, No. 15, doi:10.1186/1860-5397-3-15

• report results of our work aimed at exploring this synthetic methodology and adoption of products for the synthesis of pyrazolo[4.3-d]pyrimidines. Thus, compounds 1a-c, were prepared according to literature procedures via coupling of ethyl cyanoacetate with aromatic diazonium salts [10]. It has been

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• Intermediate with the Hydroxide Ion. A Catalytic Cycle for Peroxydisulfate Consumption. A Non-catalytic cycle for Peroxydisulfate Consumption. Oxidation of phenols Oxidation of anilines Oxidation of coumarins Oxidation of xanthones Oxidation of flavones Oxidation of pyridines Oxidation of pyrimidines Oxidation

Microwave- assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones

• Joachim C. Burbiel,
• Jörg Hockemeyer and
• Christa E. Müller

Beilstein J. Org. Chem. 2006, 2, No. 20, doi:10.1186/1860-5397-2-20

• derivatives by refluxing in HMDS, while the analogous ring closure reactions of imidazo [1,2-c]pyrimidines (e.g. 14) to the corresponding imidazo [1,2,3-cd]purine derivatives, and of pyrimido [1,6-a][1,3]diazepines (e.g. 16) to the diazepino [1,2,3-cd]purine derivatives failed under these conditions (Table 1

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium- catalyzed multi- component domino reaction

• Dipak Prajapati and
• Mukut Gohain

Beilstein J. Org. Chem. 2006, 2, No. 11, doi:10.1186/1860-5397-2-11

• Dipak Prajapati Mukut Gohain Department of Medicinal Chemistry, Regional Research Laboratory, Jorhat 785006, Assam, India 10.1186/1860-5397-2-11 Abstract Various novel pyrano [2,3-d]pyrimidines 5 and furopyrano [2,3-d]pyrimidines 7 were synthesized in 80–99% yields via a multicomponent domino

• , [19][20][21] most of which rely on multi-step reactions with yields being low. [22][23] The furo [2,3-d]pyrimidine derivatives act as useful sedatives, antihistamines, diuretics, muscle relaxants and antiulcer agents. Furthermore, pyrano [2,3-d]pyrimidines also represent broad classes of annelated

• ], we have investigated a new, simple and efficient synthesis of novel fused pyrimidines based on inverse electron-demand Diels-Alder reaction using ethyl vinyl ether/dihydrofuran and α,β-ethylenic ketones formed in situ as heterodienes in presence of 1 mol% of indium(III) trichloride (Scheme 1). This

One-pot synthesis of novel 1H-pyrimido[4,5-c][1,2]diazepines and pyrazolo[3,4-d]pyrimidines

• Dipak Prajapati,
• Partha P. Baruah,
• Baikuntha J. Gogoi and
• Jagir S. Sandhu

Beilstein J. Org. Chem. 2006, 2, No. 5, doi:10.1186/1860-5397-2-5

• ]diazepines 3 & 4 and pyrazolo [3,4-d]pyrimidines 6 were regioselectively synthesised by the reaction of 1,3-dimethyl-6-hydrazinouracils 1 with various α,β-unsaturated compounds 2 and α-ketoalkynes 8 in excellent yields. Introduction The importance of uracil and its annelated substrates is well recognized by

• heteroannulation of uracils usually require either forcing conditions[16][17] or relatively longer synthetic pathways.[18] Also, pyrazolo [3,4-d]pyrimidines are a class of naturally occurring fused uracils that possess a wide range of biological activity.[19] Allopurinol (6-dehydroxy-pyrazolo [3,4-d]pyrimidine

• -unsaturated compounds and α-ketoalkynes, which give access to an efficient unprecedented one-pot synthesis of novel pyrimido [4,5-c][1,2]diazepine-6,8-diones 3 or 4 and pyrazolo [3,4-d]pyrimidines 6 in excellent yields. A previous synthesis of pyrimido [4,5-c][1,2]diazepines reported by Mallory et al.[25