Chemically enabled synthesis of 2-amino-4-heteroarylpyrimidines

2-Amino-4-heteroarylpyrimidines were initially synthesized by microwave-induced S_NAr reactions of primary alkyl amines and 2-methylsulfonylpyrimidines or 2-chloropyrimidines. Following this methodology, pendant piperidine functionality was elaborated utilizing silica-bound reagents in microwave-assisted reductive amination and amide bond formation protocols. These methods proved to be versatile, efficient, and amenable to parallel synthesis.     

Expedient solid-phase synthesis of fluorogenic protease substrates using the 7-amino-4-carbamoylmethylcoumarin (ACC) fluorophore

A highly efficient solid-phase synthesis method for the preparation of fluorogenic protease substrates based upon the bifunctional leaving group 7-amino-4-carbamoylmethylcoumarin (ACC) is reported. Methods for the large-scale preparation of the novel fluorogenic leaving-group ACC are provided (Scheme 1). Detailed procedures are also provided for loading a diverse set of amino acids to support-bound ACC in good yields and with minimal racemization. Finally, procedures are included for the preparative synthesis of optimized ACC substrates for HIV-1 protease and plasmin.     

Use of quinolinium salts in parallel synthesis for the preparation of 4-amino-2-alkyl-1,2,3,4-tetrahydroquinoline

Compounds of pharmacological interest containing a 4-amino-2-alkyl-1,2,3,4-tetrahydroquinoline core structure were prepared starting from 4-chloroquinoline. This has been executed both in solution with a 1-benzyl-4-chloroquinolinium salt and on a solid support with a 1-(4-benzyloxybenzyl-PS)-4-chloroquinolinium resin as key intermediates. Diversification of such intermediates was accomplished through N-arylation of position 4 and subsequent nucleophilic addition of Grignard reagents of position 2 to deliver the expected 4-amino-2-alkyl-1,2,3,4-tetrahydroquinolines in 20-60% yields. The methods described within clearly demonstrate that the quinolinium salts are very efficient intermediates for parallel synthesis.     

The synthesis of 2-amino-4-tert alkylphenols

Summary The reduction of 2-nitro-4-tert-alkylphenols with sodium sulfide is described.     

Expedient synthesis of 1-vinylpyrrole-2-carbaldehydes

1-Vinylpyrrole-2-carbaldehydes and 1-vinyl-4,5-dihydrobenzo[g]indole-2-carbaldehyde were synthesized in 56-91% yields from their 1-vinyl derivatives by a modified Vilsmeier-Haack reaction. A low temperature (−78 °C) is required to avoid removal of the N-vinyl group, whereas at elevated temperature (reflux in 1,2-dichloroethane) the latter process leads to direct conversion of 1-vinylpyrroles to pyrrole-2-carbaldehydes.     

Asymmetric synthesis of 3-amino-2-hydroxy-4-phenylbutanoate

Asymmetric synthesis of 3-amino-2-hydroxy-4-phenylbutanoate, a key component of the natural product bestatin and HIV protease inhibitors of KNI-272 and R-87366, has been achieved from the stereoselective aldimine coupling reaction between 3-phenyl-2-aminopropanenitrile and (Z)-α-methoxy trimethylsilyl ketene acetal in the presence of Lewis acids.     

Rapid and efficient synthesis of 2-amino-4H-benzothiazines

The benzothiazine nucleus is a relatively unexplored class of compounds, from the standpoint of both synthetic chemistry and biological activity. We have developed a rapid, high-yielding synthesis of benzothiazines in which a precursor aryl thiourea is prepared on solid phase. Addition of trifluoroacetic acid catalyzes a conjugate addition reaction to form the desired heterocycle and releases it from the resin.     

Green synthesis and bioactivity of 2-amino-4H-chromen-4-yl-phosphonates

A simple and efficient one pot synthesis of 2-amino-4H-chromen-4-yl phosphonate derivatives has been accomplished by the condensation of salicylaldehyde, malononitrile/ethylcyanoacetate and triethyl phosphite/trimethyl phosphite in the presence of molecular iodine as catalyst in water at room temperature. All the reactions were very clean and the products were obtained in very good to excellent yields. The title compounds are characterized by IR, 1H-, 13C-, 31P-NMR and mass spectra, also studied their antimicrobial and antioxidant activity.     

Solution-phase parallel synthesis of 4,6-diaryl-pyrimidine-2-ylamines and 2-amino-5,5-disubstituted-3,5-dihydro-imidazol-4-ones via a rearrangement

The reaction of chalcones and guanidine was investigated in the presence of an oxidizing agent. Depending on the order of the addition either a 4,6-diaryl-pyrimidine-2-ylamine or 2-amino-5,5-disubstituted-3,5-dihydro-imidazol-4-one was obtained. The structures of the imidazolinones were elucidated by NMR spectroscopy and X-ray crystallography and for its formation a mechanism was proposed.     

New synthesis of 2-amino-1-thia-4-chromones

The reaction of arylacetonitriles with methyl thiasalicylate leads to 2-amino-3-aryl-1-thia-4-chromones. The spectral characteristics and the reactions at the amino group were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1047–1048, August, 1982.     

Parallel synthesis of 3-amino-4H-quinolizin-4-ones, fused 3-amino-4H-pyrimidin-4-ones, and fused 3-amino-2H-pyran-2-ones

On the basis of the enaminone methodology, libraries of 3-amino-4H-quinolizin-4-ones, fused 3-amino-4H-pyrimidin-4-ones, and fused 3-amino-2H-pyran-2-ones were synthesized by the solid-phase and by the solution-phase parallel synthesis. The solution-phase approach turned out to be advantageous over the solid-phase approach. The solution-phase synthesis afforded, in most cases, analytically pure products in high yields, whereas the solid-phase approach gave products in poor yields and in low purity.     

Solvent-free synthesis of 2-amino-4-arylthiazoles under microwave irradiation

2-Amino-4-arylthiazoles were prepared in a one-pot solvent-free procedure by reaction of p-substituted acetophenones with thiourea and iodine under microwave irradiation.     

Traceless solid-phase synthesis of 2-amino-5-alkylidene-thiazol-4-ones

2-Amino-5-alkylidene-thiazol-4-ones bearing two diversity points are prepared by a solid-phase strategy exploiting rhodanine as the starting material. Rhodanine is first loaded on bromo-Wang resin, subjected to Knovenagel condensation with aldehydes, and cleaved off the resin in a traceless manner by means of an amine.     

A convenient synthesis of 2-substituted 4-amino-5-pyrimidinecarbonitriles

Synthesis of the novel 2-halogenated 4-amino-5-pyrimidinecarbonitriles 3a,b starting from ethoxy-methylenemalononitrile 1 and cyanamide is described. Nucleophilic substitution of the reactive halogen atom leads to the derivatives 5a-g, 6 and 7a-h.     

One-pot synthesis of 3-amino-4-aryl- and 3-amino-4-hetarylfurazans

A “one pot” method for the synthesis of 3-amino-4-aryl- and 3-amino-4-hetarylfurazans from β-aryl- and 4-β-hetaryl-β-oxo acid esters was developed. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1030–1032, April, 2005.     

A base-catalyzed solution-phase parallel synthesis of substituted vinylic benzamides from 3-amino-2-cyclohexanones

An improved method for the synthesis of benzamides from 3-amino-2-cyclohexenones is presented. Using sodium hydride, a base-catalyzed N-benzoylation provided significantly higher yields (71-79%) for the reported compounds. This novel protocol was applied in the solution-phase parallel synthesis of a 12-member library of vinylic benzamide derivatives of 3-amino-2-cyclohexenones in 63-90% yield, using a Radley's Carousel Reaction Station.     

A concise synthesis of 2-chloro-3-amino-4-methylpyridine

An improved and commercially valuable process is developed for the scalable synthesis of 2-chloro-3-amino-4-methylpyridine (CAPIC), a key intermediate of Nevirapine. The synthesis was accomplished in four steps, featuring condensation starting from 4,4-dimethoxyl-2-butanone and cyanoacetamide with ammonium acetate and acetic acid as catalysts. The total yield of the process is 62.1%. The pure CAPIC sample was confirmed with FTIR, ¹H NMR, and ¹³C NMR spectra.     

Expedient synthesis of 4-O-methylhonokiol via Suzuki-Miyaura cross-coupling

Concise and practical synthesis of 4-O-methylhonokiol was achieved in 34% overall yield. The key features of our synthesis include chemoselective ortho-mono bromination of phenol as well as biaryl formation via Suzuki-Miyaura cross-coupling, in which bromophenol was reacted with potassium aryltrifluoroborate using Pd(OAc)₂ and RuPhos under microwave conditions.