Generation of 4,6-dimethyl-5-[2-(2-methylprop-1-enyl)-1H-benzimidazol-1-yl]pyrimidine-2(5H)-thiones under kinetically controlled phase transfer catalysis conditions (original) (raw)
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Journal of the Iranian Chemical Society, 2014
To date, the synthesis of various derivatives of these compounds has been reported [13-18]. The most common synthetic methods reported for the preparation of imidazo[1,2-a]pyrimidine ring systems involve closure of the imidazole ring by the condensation of 2-aminopyrimidine and closure of the pyrimidine ring by the condensation of 2-aminoimidazole with appropriate electrophilic compounds. Synthesis of imidazo[1,2-a]pyrimidines via condensation of 2-aminopyrimidine with α-halocarbonyl compounds has also been developed. The drawback of this method is difficulty in preparation, purification, toxicity, and lachrymatory property of α-halocarbonyl compounds which limit its reliability. Taking this fact into account, developing an efficient and simple route for synthesis of imidazo[1,2-a] pyrimidines is of great interest [19-24]. In our efforts to use MCRs in the synthesis of heterocycles [25-27], herein we present a multi-component and efficient route for the synthesis of novel imidazo[1,2-a] pyrimidines from the reaction of aldehydes, 2-amino-benzimidazole, and α-tetralone in the presence of catalytic amount of p-toluene sulfonic acid (Scheme 1). Experimental procedures A mixture of aldehydes (10 mmol), 2-amino-benzimidazole (10 mmol), and α-tetralone (10 mmol) with catalytic amount of p-toluene sulfonic acid (0.5 mol%) was refluxed in EtOH in appropriate reaction time. The progress of the reaction was monitored by TLC. At the end of reaction, the precipitated products were filtered and recrystallized from n-hexane: chloroform mixture (1.5:2). Characterization was performed using 1 H and 13 C NMR, FTRI, and GC techniques.
Molecules
The design of some novel di-(het)arylated-3H-pyrido[1′,2′:1,5]pyrazolo[4,3-d]pyrimidine derivatives is reported. The series was developed from 1-aminopyridinium iodide, which afforded the key intermediate bearing two thiomethyl and amide functions, each of them useful for palladium catalyzed cross coupling reactions by alkyl sulfur release and C-O activation, respectively. The two regioselective and successive cross-coupling reactions were first carried out in C-4 by in situ C-O activation and next in C-2 by a methylsulfur release. Process optimization furnished conditions leading to products in high yields. The scope and limitations of the methodologies were evaluated and the final compounds characterized.
Synthesis, 2013
Strategies for carrying out the reaction of 4,6-dichloropyrimidine-5-carboxaldehyde with both aromatic and aliphatic hydrazines to generate 1-substituted 4-chloropyrazolo [3,4d]pyrimidines in a selective, high-yielding, and operationally simple manner are presented. For aromatic hydrazines, the reaction is performed at a high temperature in the absence of an external base. For aliphatic hydrazines, the reaction proceeds at room temperature in the presence of an external base. The observed selectivity and reactivity trends are rationalized through consideration of the proposed reaction mechanism. The 1-substituted 4-chloropyrazolo[3,4-d]pyrimidine products serve as versatile synthetic intermediates, through further functionalization of the 4-chloride moiety, enabling the rapid generation of a structurally diverse array of 1,4disubstituted pyrazolo [3,4-d]pyrimidines.
Beilstein journal of organic chemistry, 2017
An efficient synthesis methodology for a series of tetrazolo[1,5-a]pyrimidines substituted at the 5- and 7-positions from the cyclocondensation reaction [CCC + NCN] was developed. The NCN corresponds to 5-aminotetrazole and CCC to β-enaminone. Two distinct products were observed in accordance with the β-enaminone substituent. When observed in solution, the compounds can be divided into two groups: (a) precursor compounds with R = CF3 or CCl3, which leads to tetrazolo[1,5-a]pyrimidines in high regioselectivity with R at the 7-position of the heterocyclic ring; and (b) precursor compounds with R = aryl or methyl, which leads to a mixture of compounds, tetrazolo[1,5-a] pyrimidines (R in the 5-position of the ring) and 2-azidopyrimidines (R in the 4-position of the ring), which was attributed to an equilibrium of azide-tetrazole. In the solid state, all compounds were found as 2-azidopyrimidines. The regiochemistry of the reaction and the stability of the products are discussed on the b...
Journal of Chemistry, 2013
Condensation of sodium 3-oxo-3-(1-phenyl-1H-pyrazol-4-yl)prop-1-en-1-olate (2) with several heterocyclic amines, cyanoacetamide, cyanothioacetamide, and 2-cyanoacetohydrazide gives pyrazolo[1,5-a]pyrimidines (5a-d), pyrido[2 ,3 :3,4]pyrazolo[1,5a]pyrimidine (9), benzo imidazo[1,2-a]pyrimidine (10), [1,2,4]triazolo[1,5-a]pyrimidine (11), and pyridine derivatives (12-14). Also, thieno[2,3-b]pyridines (15-18) were synthesized via pyridinethione (13) with -halo ketones and -halo ester. Structures of the newly synthesized compounds were elucidated by elemental analysis, spectral data, alternative synthetic routes, and chemical transformation whenever possible.
Improved synthesis of pyrrolo[1,2-c]pyrimidine and derivatives
Tetrahedron Letters, 1996
An improved synthesis of pyrrolo[1,2-c]pyrimidine derivatives by cyclocondensation of pyrrole-2carboxaldehydes with tosylmethyl isocyanide followed by desulfonylation of the resulting 2-tosylpyrrolo[1,2-c]-pyrimJdines with sodium amalgam is described Copyright © 1996 Elsevier Science Ltd We became interested in pyrrolo[ 1,2-c]pyrimidine 1 as a starting material for a straightforward synthesis of new N-bridged azole systems 3 in which one of the coplanar azole rings is positively charged by quaternization of its bridgehead nitrogen. Such systems exist as a tricyclic cation or alternatively, if internal compensation of the positive charge is accomplished, 2 as a conjugated mesomeric betaine. We hoped that either the cationic or the heterobetalne structures might exhibit interesting electronic properties associated with charge transfer between the azole-azolium moieties.
Synlett, 2012
Regioselective syntheses of 1,4,5-trisubstituted 1,2,3-triazoles were accomplished by three different strategies, relying on (i) the interception of stoichiometrically formed 5-cuprated-1,2,3-triazoles, (ii) the use of stoichiometrically functionalized alkynes or (iii) catalytic C-H bond functionalizations. This perspective article summarizes progress in this research area until June 2010.
HETEROCYCLES, 2000
Substituted 3-amino-4-oxo-4H-pyridino[1,2-α]pyrimidines (6, 7), available in 2 steps from methyl 2-benzyloxycarbonylamino-3-dimethylaminopropenoate (3) and 2-aminopyridines (1, 2), were diazotized into stable diazonium tetrafluoroborates (8, 9). Heating of diazonium salts (8, 9) with primary alcohols furnished alkyl 1-(substituted pyridin-2-yl)-1H-1,2,3-triazoles (11, 12) in 30-70% yields. Quinolizines 1 and their 1-aza analogs, pyridino[1,2-α]pyimidines, 2 are constituents of various naturally occurring alkaloids exhibiting neuroleptic 3 analgesic, 4 antiemetic, 5 antibacterial, 6 and antitumor activity. 7 On the other hand, 1,2,3-triazoles and fused 1,2,3-triazoles also represent an important class of heterocyclic compounds which have found a wide and versatile use in organic synthesis, medicinal chemistry, and industrial applications. 8 For example, 1H-1,2,3-benzotriazole is a highly efficient synthetic auxiliary 9 and numerous 1,2,3-triazole derivatives exhibit diverse biological activities, such as antiviral, 10 fungicidal, 11 muscarinic, 12 antiallergic, 13 anticoccidial, 14 anti-HIV-1, 15 antiepileptic, 16 antiinflammatory, 17 prostaglandin synthesis inhibition, 18 and others. 19 Recently, 2-substituted 3-(dimethylamino)propenoates proved to be simple and efficient reagents for the preparation of various heterocyclic systems. 20,21 For example, 3-substituted 4-oxo-4H-pyridino[1,2-]pyrimidines can be prepared in one step from 2-aminopyridines and 2-substituted 3-(dimethylamino)propenoates. 20-23 Utilization of 2-benzyloxycarbonylamino and 2-vinylamino substituted 3-(dimethylamino)propenoates made 3-amino-4-oxo-4H-pyridino[1,2-]pyrimidines available in two steps and good yields from 2-aminopyridine derivatives. 22,23 In continuation of our research in this field we studied transformations of 3-amino-4-oxo-4H-pyridino[1,2