Rhodium(III) and palladium(II) complexes of some P-heterocycles; synthesis and X-ray structures

Deoxygenation of the syn-3-phosphabicyclo[3.1.0]hexane 3-oxides bearing a 3-phenyl or a 3-(4-methylphenyl) substituent (1a,b) by trichlorosilane took place already at mild condition and resulted in the corresponding phosphines (2a,b) with retention of configuration at phosphorus, while in the case of 3-(2-methylphenyl)-3-phosphabicyclo[3.1.0]hexane (2c), the inversion of the phosphorus atom was observed in solution under ambient conditions that was evaluated by quantum chemical calculations. A further phosphine ligand (5) was obtained by the reduction of 4-dichloromethylene-1,4-dihydrophosphinine oxide (4). The phosphine ligands (2 and 5) were used in the preparation of Rh(III) complexes (3 and 6). A Pd(II) complex of type PdCl₂(5)₂ (7) was also prepared. The stereostructures of a series of Rh(III) complexes of 3-aryl-3-phosphabicyclo[3.1.0]hexanes (3b-syn, 3c-syn and 3c-anti) were elucidated by single crystal X-ray analysis confirming the relative position of the dichlorocyclopropane and the P-substituent.     

Preparation,isomerisation et configuration absolue des “hydrates” de thymidine

The (+) and (?) cis-6-hydroxy-5,6-dihydrothymidines 4a and 5a have been prepared by mild reduction of (+) and (?) trans-5-bromo-6-hydroxy-5,6-dihydrothymidine 2a and 3a. The trans “hydrates” 6a and 7a have been prepared by warming 4a or 5a in alkaline aqueous solution at 60°C. The isomerization of 4a, 5a, 6a and 7a involved the opening of the pyrimidine ring at 1,6 position and subsequent keto-enolisation. The characterization of the configurations of “hydrates” is based on the specific formation of the enantiomeric forms of 6-hydroxy-5,6-dihydrothymine by radiation-induced degradation of 4a, 5a, 6a, 7a and 5,6-dihydrothymine 5S8b.     

Functionalized enamines—XXII : Annelation of enamines of polycyclic α,β-unsaturated ketones; a facile partial synthesis of furano- indolo- and benzsteroids. Total synthesis of 3-oxa-A-norsteroid

Reaction of dienamine 4a with substituted phenacyl bromides gave steroidal[3,4-b] furans 5a–g. The same principle reaction was utilized for the total synthesis of (±) 2 - (p - chlorophenyl) - 3 - oxa - A - nor - estra - 1,5(10), 9(11) - triene - 17 - acetate 12a. Treatment of 4a, b with benzenediazonium salts, in DMF, followed by a Fischer-indole cyclization yielded steroidal[6, 7-b] indoles 8a–k. Dienamine 4b could be annelated to benz[4, 5, 6] steroids 9a and 9b by reaction with methyl vinyl ketone and crotonaldehyde, respectively.     

Asymmetric catalysis. Part 153: Metal-catalysed enantioselective α-ketol rearrangement

Promoted by catalytic amounts of Ni complexes tertiary α-hydroxyketones 1a, 3a–5a undergo rearrangement, forming chiral isomers 1b, 3b–5b. The best enantioselection was obtained with the model system 1-benzoylcyclopentanol 4a/2-hydroxy-2-phenylcyclohexanone 4b. In a ligand screening 2-[4-(S)-tert-butyloxazolin-2-yl]pyridine gave the highest enantiomeric excess of 46% (S)-4b. The analogous isomerisation reactions of α-hydroxyimines 6a, 7a forming chiral α-aminoketones 6b, 7b were established.     

Synthesis of 4-aryl-substituted β-lactam enantiomers by enzyme-catalyzed kinetic resolution

Enantiopure 4-phenyl- and 4-(p-tolyl)-2-azetidinones 3a, 3b, 4a and 4b (with e.e.s of ≥96%) were prepared through lipase-catalyzed asymmetric butyrylation of the primary OH group of N-hydroxymethylated β-lactams (±)-5 and (±)-6 at the (R)-stereogenic centre or by lipase-catalyzed asymmetric debutyrylation of O-butyryloxymethyl-2-azetidinones (±)-7 and (±)-8 at the (R)-stereogenic centre. The ring-opening of lactams 5a, 5b, 6b and 8a with HCl/EtOH afforded the corresponding β-amino ester enantiomers 9a, 9b, 10a and 10b with e.e.s of ≥92%.     

Synthesis of functionalised cephalosporins : Diphenylmethyl(1S,6R,7S)-3-bromomethyl-7-formamido-7-methoxyceph-3-em-4-carboxylate-1-oxide: a useful intermediate in the preparation of 7α-methoxycephalosporins

The N-formamido cephalosporins 4a and4b undergo direct methoxylation at the Pα-position to give the 7α-methoxy derivatives 5a and 5b. These were converted to other 7β-acylamido compounds by the sequence : oxidation, deformylation, acylation and reduction. The 3-bromomethyl derivatives 2b,6b and 8b proved amenable to nucleophilic substitution with 5-mercapto-1-methyltetrazole.     

Synthesis of arylated highly congested indans using a domino sequence

A novel and efficient regioselective synthesis of various arylated highly congested 7-aryl-5-methylsulfanylindan-4-carbonitriles (3a-f), methyl 7-aryl-5-methylsulfanylindan-4-carboxylates (10a-e) and 7-aryl-5-methylsulfanylindan-4-carboxylic acids (11a-e) through base-catalyzed reaction of 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (1a-f) and methyl 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (9a-e) by cyclopentanone (2) has been delineated. The synthetic potential of 2-pyranone was explored further to generate molecular diversity using 6-aryl-4-sec-amino-2-oxo-2H-pyran-3-carbonitriles (7a-h), 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (5a,b) and methyl 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (12a,b) as precursors for the ring transformation by cyclopentanone to assess the effects of substituents on the course of the reaction to obtain highly congested indans, 6,7-diaryl-5-methylsulfanylindan-4-carbonitriles (6a,b), 7-aryl-5-(piperidin-1-yl)indan-4-carbonitriles (8a-h) and methyl 6,7-diaryl-5-methylsulfanylindan-4-carboxylates (13a,b).     

17α-Konfigurierte 20-methylpregnan-derivate

A mixture of 1a+1b (17α), obtained by C-17-epimerization of pregnenolone (1a) was converted into 3a+3b by Wittig-reaction. 3a+3b were acetylated to a mixture of 4a+4b, from which 4b was isolated by cristallization of 3a and following AgNO₃-chromatography of the mother-liquors. Δ²⁰⁽²²⁾ → Δ¹⁷-doublebond-isomerization occurs by hydrogenation (Pd/C) of 3a (17β) to give 5. Hydrogenation (Pt-catalyst) of 4b (17α) leads to 8b, which was converted into the 20-methylpregnane-derivatives 7b, 9b–13b. By comparison with the 17β epimers 1a–4a, 7a–13a a spectroscopic determination of the relative configuration on C-17 of 17-alkylsubstituted steroids was possible.     

Nucleophilic subsitution at silicon: Synthesis of sterically-hindered bis(2,6-di-t-butylaryloxy)silanes

The reaction of the monomethylsilane (8a) with two equivalents of the 4-(carboalkoxy)-2,6-di-t-butyl-substituted phenol (7b) in toulene using triethylamine as an acid acceptor gave the bis(aryloxy) adduct (9a). The analogus reaction of the dimethylsilane (8b) with sodium 2,6-di-t-butyl-4-(methoxycarboxyl)-phenolate (7a) gave only the monosubstitution product (10a). The reaction of the corresponding phenolate (7e) with 8b gave a mixture of 7a, 10a, and bis-adduct (9b), whereas, in the presence of 15-crown-5, the bis-adduct 9b was obtained. The bis-adducts 9c–e were prepared in an analogous manner. The reaction of n-hexyl 3,5-di-t-butyl-4-hydoxylbenzoate (7h) with the diphenylsilane (8c) gave only the monosubstitution product 12, while forcing conditions gave, unexpectedly, the methyl ether 13. The reaction of 4-(carboalkoxyethyl)-2,6-di-t-butylphenol (16a) with 8a gave the bis adduct. The reaction of 16a with 8b in THF, without a crown ether, gave a low yield of the monosubstitution product. The bis-adducts 17b–c were obtained by the reaction of 8b with the corresponding phenolates (16a–b) in tetraglyme. Compound 17b was also obtained by the reaction of 8b with 16a in THF with a crown ether. These results are discussed in terms of charge dispersal in the phenolate ion and the corresponding effect upon both ion-pairing and aggregation in solution.     

Enamine chemistry—XXV: Reduction of enaminones by LiAlH4 and NaBH4. Synthesis of α,β-unsaturated aldehydes

Cyclohexanone, 2-methyl-cyclohexanone and 4-methyl-cyclohexanone, 1, were transformed into the enaminones 4a–4e by the following two routes: (A): Acylation of the enamines, 2, derived from 1 and secondary amines (pyrrolidine, morpholine and piperidine) by ethyl chloroformate, and (B): Condensation of 1 with diethyl oxalate, giving the β-ketoesters 3, followed by reaction with the secondary amines. Ethyl 2(-1-pyrrolidinyl)-1-cyclopentene-1-carboxylate, 4f, and methyl 3-(1-pyrrolidinyl)-2-butenoate, 4g, were prepared from ethyl 2-oxo-1-cyclopentanecarboxylate and ethyl 3-oxo-butanoate, respectively, by condensation with pyrrolidine. Reduction of 4a by LAH afforded 1-cyclohexen-1-carboxaldehyde, 5a, 1-cyclohexene-1-methanol, 6a, and 1-(1-cyclohexene-1-methyl)pyrrolidine, 7a, in yields depending on the molar ratio of LAH/4a. Reduction of 4f by LAH gave cyclopentene-1-methanol, 6b, 1-(1-cyclopentene-1-methyl)pyrrolidine, 7b, and ethyl-2(1-pyrrolidinyl)-1-cyclo-pentanecarboxylate, 8b. Compound 4g, when reduced with LAH, yielded methyl 3-(1-pyrrolidinyl) butanoate, 8c (main product) and 1-(2-butenyl)pyrrolidine, 7c (minor). Reduction of 4 by NaBH₄ afforded exclusively the saturated β-aminoesters, 8 in high yields. The reductions with LAH and NaBH₄ are rationalized in terms of the HSAB principle.     

Stereospecific synthesis of some polycyclic cis-β-lactams

Amides 1 on reaction with P₂S₅ in pyridine give thioamides 2 which on treatment with methyl iodide afford the corresponding 1-methylthio-3,4-dihydroisoquinolines 3. Annelation of these imines with phenoxyacetyl chloride in the presence of triethylamine furnish 6-methylthio-7-phenoxy-2',3' - dimethoxybenzo[a]octem 4a and 6-methylthio-7-phenoxy-2,3-methylenedioxybenzo[a]octem 4b respectively. Desulphurisation of these β-methylthio-β-lactams with Raney nickel yield the novel polycyclic cis-β-lactams 5a and 5b.     

Novel thiosemicarbazone derivatives containing benzimidazole moiety: Green synthesis and anti-malarial activity

A series of (E)-2-[5-chloro-1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (7a–7t) and (E)-2-[1-(1H-benzo[d]imidazol-2-yl)ethylidene] N-(substituted) hydrazine carbothioamide (8a–8t) were prepared via the synthesis of 1-(substituted-1H-benzimidazol-2-yl) ethanol (3a–3b) which was synthesized by the condensation of substituted o-phenylenediamine (2a–2b) with dl-lactic acid (1) followed by oxidation with sodium hypochlorite in mild acidic condition to form the corresponding ketones 4a–4b. Final compounds were formed by condensation of 4a–4b with different thiosemicarbazides 6a–6t. A total of 40 compounds were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, Mass spectral technique and elemental analysis, in addition they were evaluated for anti-malarial properties. Among the compounds tested 7o, 7p, 7q, 7r, 7s, 8e and 8h exhibited good antimalarial activity in vitro.     

Studies on organophosphorus compounds—XXXVII: Syntheses of δ5-1,2,3-diazaphospholines and indoles from hydrazones

2,4-Bis(4-methoxyphenyl-1,3,2,4-dithiadiphosphetane-2,4-disulfide, 1, reacts with phenylhydrazones of methylketones to give Δ⁵-1,2,3-diazaphospholines, 3; in one case 2-methyl-3-phenylindole, 4, was also isolated. Phenylhydrazones of cyclopentanone and cyclohexanone similarly yield the corresponding annulated P-heterocycles, 6a, 6b and as by-products the indoles 7a and 7b, respectively. The sole product from the reaction of 1 with the phenylhydrazone of 1,3-diphenyl-2-propanone is 2-benzyl-3-phenylindole, 9. A mechanism for the formation of the diazaphospholines is suggested.     

Synthesis of nicotinonitrile derivatives as a new class of NLO materials

4,6-Diaryl-2-(pyrrolidin-1-yl)-nicotinonitriles 2a-k and 3-amino-2,4-dicyano-5-aryl-biphenyls 3a-c were synthesized from 1,3-diaryl-prop-2-en-1-ones 1a-k and malononitrile by a convenient one-pot method. Likewise, the reaction of aromatic aldehydes with malononitrile afforded 6-amino-4-aryl-2-(pyrrolidin-1-yl)-pyridine-3,5-dicarbonitriles 6a-f. The reaction of mesityl oxide with malononitrile gave 5-amino-7-(pyrrolidin-1-yl)-2,4,4-trimethyl-1,4-dihydro-1,6-naphthyridine-8-carbonitrile 8. The NLO studies of the pyridinedinitrile derivatives 6a, b, f showed a high value while that of nicotinonitrile 2b was weak.     

Regioselective synthesis of 2,5-dihydro-4H-pyrazolo[4,3-c]quinolin-4-ones by the cyclization of 3-acyl-4-methoxy-1-methylquinolinones with hydrazines

Reaction of 3-acyl-4-methoxy-1-methylquinolinones 2 and 5 with hydrazines has been investigated under different experimental conditions. Compound 2 always gave rise selectively and exclusively to the regioisomeric 1,3-disubstituted- or 2,3-disubstituted-pyrazolo[4,3-c]quinolin-4(5H)one (compounds 3a,b or 4a,b, respectively), while reaction of 5 with N-methylhydrazine led to a mixture of pyrazoles 7a and 8a. With N-phenylhydrazine, compounds 7b or 8b were regioselectively obtained. Compound 8a could be selectively synthesized working in solventless conditions. Structural elucidation of all products was independently achieved by NMR spectroscopy.     

Synthesis of New Potential Hydrophobic Agents Composed of Three-Module Type Molecules

A new synthetic route was developed to three-module type potential hydrophobic agents, with the molecule consisting of an N-[3-(triethoxysilyl)propyl]amide anchor part (I), a connecting unit formed upon 1,3-propansultone ring cleavage (II), and a polyfluoroheptyloxy functional hydrophobic spacer (III). Proceeding from commercially available polyfluorinated heptanols 1a and 1b and 1,3-propanesultone 3, potassium sulfonates 4a and 4b were prepared. The reaction of 4a and 4b with phosphorus oxychloride resulted in the first synthesis of fluorine-containing sulfonyl chlorides 5a and 5b, which were reacted with 3-aminopropyltriethoxysilane 6 to give the target N-[3-(triethoxysilyl)propyl]-3-(polyfluoroheptyloxy)propane-1-sulfonamides 7a and 7b. The structures of the compounds were proved by NMR spectroscopy, mass spectrometry, and elemental analysis. The studies of their hydrophobizing properties are in progress.     

Functionalized enamines—XV: Reactivity patterns of carbene addition to morpholine enamine of 1-β-acetoxy-6-oxo-8a-methyl-Δ4a(5)-octalin

Carbenes3a-e add to the α-side of the first double bond of dienamine2 (title compound) to give 1 : 1 adducts4a-e, Chlorofluorocarbene3e gives, in addition, ketone7, corresponding to β-addition at the second double bond of2, and a 2 : 1 adduct8. The reaction of2 with dichlorocarbene3a yields, besides4a, novel ring-expansion products5 and6 corresponding to addition of two moles of3a. Ethoxycarbonylcarbene3f reacts with the dienamine (2) to give isomeric esters9 and10a,b. The structure assignments and the mechanism of formation of the reaction products are discussed.     

Photochemical desulfurization of l-cysteine derivatives

Thiol groups can be reductively eliminated at room temperature by a photochemical method which makes use of triethylboron, triethylphosphite and visible light. Thus, after treating l-Cys 1a, d-Pen 1b, l-Cys-OMe 1c and glutathione (γ-l-Glu-l-Cys-Gly) 3, the corresponding desulfurized compounds l-Ala 2a, d-Val 2b, l-Ala-OMe 2c and γ-l-Glu-l-Ala-Gly 4, respectively, are prepared in high yields and with retention of configuration.     

Pyrido[2,3-d]pyrimidines,II. One step synthesis of pyrido[2,3-d]pyrimidines and pyrimido[4,5-b]quinolines from 6-amino uracils

Summary Reduction of 6-azidouracils2 with hydrogen palladium or sodium dithionite afforded the corresponding 6-aminouracils5 which could also be obtained by reaction of2 with triphenylphosphanevia phosphazenes and subsequent hydrolysis (Staudinger reaction). The use of trimethylphosphite instead of phosphanes yields with2b the expected trimethoxyphosphazene3c, whereas2a reacts to the phosphonoaminopyrimidine4. The syntheses of 5-hydroxy pyrido[2,3-d]pryimidine-2,4,7-triones6, pyrido[2,3-d]pyrimidine-2,4,5-triones8, cyclopenta[e]pyrido[2,3-d]pyrimidin-2,4,5-triones7a,c, and tetrahydro-pyrimido[4,5-b]quinolin-2,4,5-triones7b,d by condensation of 6-aminouracils5 with malonates, ethylaceto/benzoylacetate, ethyl 2-oxocyclopentanecarboxylate and ethyl 2-oxocyclohexanecarboxylate, respectively, are described.

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Pyrido[2,3-d]pyrimidine, 2. Mitt. Einstufige Synthese von Pyrido[2,3-d]pyrimidinen und Pyrimido[4,5-b]chinolinen aus 6-Aminouracilen

Zusammenfassung Reduktion der 6-Azidouracile2 mit Wasserstoff/Palladium oder Natriumdithionit ergibt die entsprechenden 6-Aminouracile5, die auch durch Reaktion von2 mit Triphenylphosphin und anschließende Hydrolyse erhalten werden können (Staudinger-Reaktion). Die Verwendung von Trimethylphosphit anstelle von von Trimethylphosphin ergibt mit2b das erwartete Trimethoxyphosphazin3c, während2a zum Phosphonoaminopyrimidin4 reagiert. Die Synthesen der 5-Hydroxy-pyrido[2,3-d]pyrimidin-2,4,7-trione6, der Pyrido[2,3-d]pyrimidin-2,4,5-trione8, der Cyclopenta[e]pyrido[2,3-d]pyrimidin-2,4,5-trione7a,c und der Tetrahydro-pyrimido[4,5-b]chinolin-2,4,5-trione7b,d durch Kondensation der 6-Aminouracile5 mit Malonat, Acetat, Ethyl-2-oxocyclopentancarboxylat und Ethylcyclohexancarboxylat werden beschrieben.

     

Carbon-nitrogen bond formation in the reaction of the reaction of diphenyl diazomethane Ph2 CN2 with diiron-carbene complexes (Fe2(CO)7x03BD;-C(R)C(NEt2)x03BD;-C(R)C(NEtx03BC;-C(R)C(NEt2)N(NCPh2)x03BC;-C(R)C(NEtx03BC;-C(R)C(NEt2)NN(CPh2)x03BC;-C(R)C(NEt)]

The diiron ynamine complex [Fe₂(CO)₇{μ-CR)C(NEt₂)}] (1:R=Me,2:R = C₃H₅.3:R=SiMe₃.4:R = Ph) reacts at room temperature with diphenyldiazomethane Ph₂CN₂, in hexane to yield complexes [Fe₂(CO)₆{C(R)C(NEt₂)N (NCPh₂)] (5a:R=Me,6a:R=C₃H₅.7a R=SiMe₃.8a:R=Ph) resulting from the insertion of the terminal nitrogen atom into the Fe=C carbene bond. Insertion the second nitrogen atom and formation of compounds [Fe₂(CO)₆zμ-C(R)C(NEt₂)NN(CPh₂)}] (5b:R=Me,6b:R=C₃H₅,7b:R=SiMe₃,8b:R=Ph) is observed when compounds5a-5a are treated in refluxing hexane. Transformation of compoundsa tob is also obtained at room temperature within a few days. All compounds were identified by their¹H NMR spectra. Compounds6a, 7a, 8a, and8b were characterized by single crystal X-ray diffraction analyses. Crystal data: for6a: space group = P2₁/n,a=12.853(1) A,b=24.800(7) A,c=8.947(6) A,β=99.29(3)°,Z=4, 2227 rellectionsR=0,038; for7a: space group=Pl,a=ll.483(4) A,b=14.975(4) A,c = 17.890(8) A,α = 82.80(3)°,β=94.29(7)°,γ=85.42(2),Z = 4, 5888 reflectionR = 0.035: for8a: space group = Pcab.a = 31.023(8) A.b=20.137(1) A.c=9.686(2) A.Z=8. 1651 reflections,R=0.071; for8b: space group=P2₁/n,a=21.459(4),b=10,100(3) A,c=28,439(8) A,ß=103.86(4)°,Z=8. 2431 reflections.R=0.057.