Highly enantioselective sequential hydrogenation of ethyl 2-oxo-4-arylbut-3-enoate to ethyl 2-hydroxy-4-arylbutyrate

The hydrogenation of (E)-ethyl 2-oxo-4-arylbut-3-enoate with [NH2Me2](+)[{RuCl [(S)-SunPhos]}2(mu-Cl3)] gave ethyl 2-hydroxy-4-arylbutyrate with 94-96% ee. Further investigation has proved that the hydrogenation proceeded via a sequential hydrogenation of CO and CC bonds, which is sensitive to the reaction temperature. Hydrolysis of ethyl 2-hydroxy-4-phenylbutyrate (ee 93%) provided the 2-hydroxy-4-phenylbutyric acid with 81% yield at 99% ee after a single recrystallization from 1,2-dichloroethylene.     

Regioselective palladium-catalyzed phenylation of ethyl 4-oxazolecarboxylate

The efficient and regioselective palladium-catalyzed C-2 arylation of ethyl 4-oxazolecarboxylate 1 with phenyliodide is described. The different parameters (solvent, base, ligand and catalyst) for the optimal conditions of this arylation process have been screened.     

The reaction of ethyl 4H-pyran-4-one-2-carboxylate with 1,2-diaminobenzene

Ethyl 4H-pyran-4-one-2-carboxylate was allowed to react with 1,2-diaminobenzene and related diamines. The resulting products were found to be 8H-5,6-dihydro-6,8-dioxopyrido[1,2-a]quinoxaline and derivatives. The synthesis 3H-5,6-dihydrobenzo[g]pyrido[1,2-a]quinoxaline-3,5-dione ( 2c ) constitutes the synthesis of a derivative of previously unknown benzo[g]pyrido[1,2-a]quinoxaline ring system.     

Immobilized microorganisms in the reduction of ethyl 4-chloro acetoacetate

Microorganisms were used to reduce ethyl 4-chloroacetoacetate (CAAE) to ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE]. Mucor ramannianus provided 98% conversion with 84% ee. Free cells of Kluyveromyces marxianus led to 95% conversion with 81% ee. After a fractionary factorial design to study the reaction conditions, calcium alginate immobilized cells of K. marxianus furnished the product with 99% conversion with 91% ee.     

Synthesis of S-[2-(4-Aminobenzenesulfonyl)ethyl] and S-[2-(3-Amino-4-methoxybenzenesulfonyl)ethyl] Thiosulfonates

Russian Journal of General Chemistry -     

Reactions of 2- and 4-methylpyrylium salts with ethyl orthoformate

Under mild conditions 2- and 4-methylpyrylium salts react with ethyl orthoformate to give their β-ethoxyvinyl derivatives. Symmetrical and unsymmetrical cyanine dyes were synthesized by heating the latter with 2- and 4-methylpyrylium salts or N-methylquinaldinium perchlorate. The pyrylocyanines react with perchloric acid to give bispyrylium salts, and they are converted to the corresponding pyridine bases by the action of ammonium acetate.     

Efficient one-pot synthesis of ethyl 2-substitued-4-methylthiazole-5-carboxylates

A new and practical one-pot procedure for the synthesis of several 2-sustituted-4-methylthiazole-5-carboxylates from commercially available starting materials is described. Under mild reaction conditions, some of the products with alkyl group on the 2-amino group or with various groups on 2-substituted phenyl ring were obtained in good yields from ethyl acetoacetate, N-bromosuccinimide, thiourea, or its N-substituted derivatives in an efficient way instead of the traditional two-step reaction.     

Stereospecific microbial reduction of ethyl 1-benzyl-3-oxo-piperidine-4-carboxylate

Microbial reduction of ethyl 1-benzyl-3-oxo-piperidine-4-carboxylate by the majority of evaluated microorganisms gave the ethyl cis-(3R,4R)-1-benzyl-3R-hydroxy-piperidine-4R-carboxylate as the major product in high diastereo- and enantioselectivities. The 3R,4R-hydroxy ester was produced in 97.4% diastereomeric excess (de) and 99.8% enantiomeric excess (ee) by Candida parapsilosis SC16347, while 99.5% de and 98.2% ee were obtained from reduction by Pichia methanolica SC16415. A few of the evaluated microorganisms gave 10–40% of the ethyl trans-(3R,4S)-1-benzyl-3R-hydroxy-piperidine-4S-carboxylate as the minor product.     

Total,asymmetric synthesis of ethyl d-ido-4-heptulosuronate derivatives starting from diethyl 4-oxopimelate

Bromination of diethyl 4-oxopimelate, followed by double elimination of HBr and ketalization provided diethyl (E,E)-4,4-(ethylidenedioxy)hepta-2,5-dienedioate 4. Sharpless asymmetric dihydroxylation of 4 produced diethyl (2S,3S)-4,4-(ethylidenedioxy)-2,3-dihydroxyhept-5-enedioate (+)-5, with 78% e.e. The corresponding tetrol could not be obtained in one step. Silylation of (+)-5 and a second asymmetric dihydroxylation, followed by silylation led to 20% of meso-diester 9 and 60% of diethyl (2S,3S,5S,6S)-2,3,5,6-tetrakis[(t-butyl)dimethylsilyloxy]-4,4-(ethylidenedioxy)heptanedioate (−)-10. Reductive desymmetrization of (−)-10 with DIBAL-H furnished, after selective oxidation, ethyl (2S,3S,5S,6S)-2,3,5,6-tetrakis-[(t-butyl)dimethylsilyloxy]-4,4-(ethylidenedioxy)-7-oxoheptanoate (+)-13 which was then converted into ethyl 1,2,3,6-O-tetraacetyl-4,4-ethylidenedioxy-α- and β-d-ido-heptapyranuronate (−)-15α,β and into the corresponding 3-(α-d-pyranosyl)propene (−)-16.     

N-1 Substituted ethyl 4-pyrazolecarboxylates: Synthesis and spectroscopic investigations

The synthesis of various N-1 substituted ethyl 4-pyrazolecarboxylates via reaction of ethyl 2-formyl-3-oxo-propionate (= ethoxycarbonylmalondialdehyde) with appropriately substituted hydrazines is described. Moreover, detailed nmr-spectroscopic investigations with the title compounds are presented.     

4-二甲胺苯酰甲酸乙酯的合成及反应副产物的分离鉴定

α-酮酸酯是重要的有机合成中间体。前文报道了以Grignard试剂与草酸二乙酯反应,合成一系列脂肪族α-酮酸酯的方法。为了进一步了解和掌握这一方法,我们研究了合成4-二甲胺基苯酰甲酸乙酯(1)的反应。1的收率随反应温度、溶剂及原料配比的不同而有显著差别。在本文报道的条件下,收率高达90％。此外,从反应混合物中还分得了2-羟基-2,2-双(对-二甲胺基苯基)乙酸乙酯(2),4,4’-双(二甲胺基)-二苯基乙二酮(3),2-羟基-1,2,2-三(对-二甲胺基苯基)乙酮(4)及4,4’-双(二甲胺基)联苯(5)等副产