A FACILE CONVERSION OF THE BAYLIS-HILLMAN ADDUCTS INTO TRIMETHYLSILYL ETHERS WITH HEXAMETHYLDISILAZANE CATALYSED BY IODINE

The hydroxy group of the Baylis-Hillman adducts was protected with trimethylsilyl (TMS) group using the reaction of adducts 1a–h with hexamethyldisilazane (HMDS) catalyzed by iodine under nearly neutral reaction conditions.     

Stereospecificity of Diels–Alder Reactions Validated Using Ab Initio Calculations: Synthesis of Novel Coumarin and Phenanthridine Derivatives

A new series of coumarin derivatives (2–5) was synthesized by reaction of phenylsulfonylacetonitrile (1) with 2-hydroxy-1-naphthaldehyde and/or salicyaldehyde. Compounds 3 and 5 were converted to the corresponding phenanthridine analogs 6 and 7, respectively. Compound 9a was treated with different dienophiles to furnish the endo adducts of compounds (11a–d) rather than the exo adducts. Ab initio calculations at the Hartree-Fock (HF) level using the basis set 6-31 G (d,p) was used to study and validate the stereospecificity of compounds 11a–d and showed clearly that the endo adducts were thermodynamically favorable. PM3 parameters also showed that the endo adducts are thermodynamically and kinetically favorable. Tetrahydrobenzochromenone (11) was synthesized and allowed to react with different aromatic diazonium salts to give the corresponding 4-arylazo derivatives (13), which were converted to the corresponding diazaindenophenanthrene derivatives (14) by reaction with o-diamines.     

AN EASY CONVERSION OF THE BAYLIS-HILLMAN ADDUCTS INTO tert-BUTYLDIMETHYLSILYL ETHERS WITH tert-BUTYLDIMETHYLSILYL CHLORIDE AND Li2S

The hydroxy group of the Baylis-Hillman adducts is protected with the t-butyldimethylsilyl (TBDMS) group using the reaction of adducts 1a–h with tert-butyldimethylsilyl chloride (TBDMSCl) in the presence of lithium sulfide under nearly acidic reaction conditions.     

OLEFIN SYNTHESIS VIA THE LITHIUM DERIVATIVES OF THE N,N,N,N′-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS. 2. SYNTHESIS OF SOME (Z)-ORTHO-AND PARA-SUBSTITUTED STILBENES

Abstract

The reaction of the lithium derivatives of N,N,N′,N′-tetramethyldiamides of arylmethanephosphonic acids (1-Li) with ortho- and para-substituted benzaldehydes 2 is studied. Reaction conditions are found for erythro-stereoselective addition of 1 to 2 with high diastereomeric purity (95–99%) of the erythro adducts 3, 4 (yields 35–72%). By thermolysis of the adducts in neutral medium the corresponding (Z)-ortho and para-substituted stilbenes 5, 6 are obtained. Some factors causing the predominant formation of the erythro adducts 3, 4, as well as the influence of the ortho-substituents on the equilibrium threo-3, 4 ? erythro-3, 4 are discussed.     

OLEFIN SYNTHESIS VIA THE LITHIUM DERIVATIVE OF THE N,N,N′,N′-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS. 3 SYNTHESIS OF SOME β-DISUBSTITUTED STYRENES

Abstract

The reaction of Li-derivatives of N,N,N′,N′-tetramethyldiamides of arylmethanephosphonic acids (1-Li) with alkanones, cycloalkanones, alkylaryl-and diarylketones 2a-h is studied. It is found that in THF at-70°C adducts 3-Li and 4-Li are formed, the corresponding hydroxyl compounds 3 and 4 being isolated in 36–81% yields, while by elevated temperatures the reaction is completely shifted to the starting 1-Li and 2. By thermolysis of 3 and 4 in neutral medium olefins 5 and 6 are obtained even from readily enolysable ketones. The stereochemistry of the addition reaction with nonsymmetrical ketones as well as the influence of the substituents at the carbonyl groups on the conformation and adsorption properties of the adducts are discussed.     

One-Pot Stereoselective Synthesis of Alkyl Z-2-[2-Amino-4-oxo-1,3-selenazol-5(4H)-yliden] Acetates

Abstract

Selenourea reacts with dialkyl acetylenedicarboxylates in acetone to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-selenazol-5(4H)-yliden) acetates in fairly good yields. The reaction is completely stereoselective.     

Synthesis of Dihydro- and Tetrahydro-1,2,4,5-tetrazines from the Reaction of Nitrilimines with 1-Substituted-1-methylhydrazine

Abstract

The reaction of nitrilimines (2) with 1-substituted-1-methylhydrazines (3–6) led to the formation of the respective amidrazones (7) when R = CH₃, Ph, and to the acyclic adducts (8,9) when R = CHO and COCH₃. The acyclic adducts underwent thermal oxidative cyclization at CH₃ to give the unexpected 1,2,4,5-tetrazines (10,11). Dihydro-l,2,4,5-tetrazines (12) were also seperated when R = CHO.     

PHOSPHONIUM YLIDS-VII. SYNTHESIS OF A NEW TYPE OF YLID PHOSPHORANE BY THE ACTION OF WITTIG REAGENTS ON (E)-2-BENZYLIDENEOXAZOLIDINE-4,5-DIONE

Abstract

The reaction of (E)-2-benzylideneoxazolidine-4,5-dione (1) with the methylenetriphenylphosphoranes (2) afforded new ylid-phosphoranes of type 3. The mechanism that accounts for formation of adducts 3 is discussed. Structural reasoning for compounds 3 was based on compatible analytical, chemical and spectroscopic results.     

Facile Synthesis of 4‐Functionalized Cyclopentenones

1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way.     

STUDIES ON PHOSPHONIUM YLIDS‐VIII. WITTIG REACTION WITH N,N′-3,5-CYCLO-HEXADIENE-1,2-DIYLIDENEBIS[BENZAMIDE]

Abstract

The reaction of methylenetriphenylphosphoranes (1) with N,N′-3,5-cyclohexadiene-1,2-diylidenebis [benzamide] (2) afforded new ylid-phosphoranes of type 3. The mechanism that accounts for formation of adducts 3 is discussed. Structural reasoning for compounds 3 was based on compatible analytical, chemical and spectroscopic results.     

Syntheses of Phencyclone Analogues. Applications for NMR Studies of Hindered Rotations and Magnetic Anisotropy in Crowded Diels–Alder Adducts

Undergraduate organic chemistry special laboratory projects based upon the synthesis of phencyclone, 1 (a potent Diels-Alder diene), and the preparation of a series of highly hindered Diels-Alder adducts of the phencyclone, were described earlier. Details of the synthesis of an analogue of 1 are presented here as an extension of these projects. The analogue, 3,6-dibromophencyclone, 2, and adducts from a wide range of dienophiles, can be prepared by undergraduate organic chemistry students. These adducts (from 1 or 2) are eminently suitable for student characterization by NMR to examine aspects of hindered rotation, magnetic anisotropy, and dynamic NMR spectroscopy, using modern one- and two-dimensional multinuclear methods with a medium-field instrument (7 T), to observe ¹H, ¹³C, and ¹⁹F. Use of 2 effectively doubles the range of potential target compounds for students. The Diels-Alder adducts (and their precursors) have been studied by molecular modeling methods. This present paper describes the reaction of 2 with 4, the dienophile N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (Tuppys maleimide), to form the adduct 5. Compound 5 has been well-characterized by 1D and 2D ¹H and ¹³C NMR, and is illustrative of the wide range of adducts that can be made from 2 by students. The structure of 5, as determined by geometry optimization at the semiempirical (AM-1) level, is included here.     

The First Examples of 1-Aza-3-phosphabenzenes

Abstract

The hitherto unknown 1-aza-3-phosphabenzenes are obtained via regiospecific Diels-Alder reaction with inverse electron demand of 2-trifluormethyl-4-methyl-6H-1,3-oxazin-6-on with phosphaalkynes. The primary cycloaddition adducts extrude carbon dioxide under the reaction conditions (80°C, no solvent, 3 days in a sealed tube) and cannot be isolated. The resulting 1-aza-3-phosphabenzenes are relatively stable compounds and are completely spectroscopically characterized.     

THE DIELS-ALDER REACTION OF DIPHENYL(1,2-PROPADIENYL)PHOSPHINE OXIDE AND DIPHENYL(1-PROPYNYL)PHOSPHINE OXIDE WITH CYCLOPENTADIENE

The Diels-Alder reaction of diphenyl(1,2-propadienyl)phosphine oxide 1 and diphenyl(1-propynyl)phosphine oxide 2 with cyclopentadiene is reported. 1 reacts smoothly at room temperature in the presence of one equivalent of aluminum trichloride to give the corresponding adducts endo 3a and exo 3b (90:10 ratio) whose structure was attributed on the basis of their ¹³C NMR spectra, whereas 2 is a poor dienophile, affording the corresponding adduct in low yield even under harsh conditions.     

The Quantitative Removal and Recovery of Chlorine and Bromine from Air Streams with 2,1,3-Benzoselenadiazole

Abstract

The affinity of 2,1,3-Benzeneselenadiazole (piaselenole) for dimeric chlorine and bromine has been investigated. A 1:1 adduct is formed between piaselenole and both molecular C1₂ and Br₂. At slow flow rates, piaselenole quantitatively removes halogens from contaminated air strcams. The adducts, upon reaction with water or gentle heating in an oil solution, liberates the halogen and regenerates the piaselenole.     

OLEFIN SYNTHESIS USING LITHIUM DERIVATIVES OF N,N,N',N'-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS

Abstract

The reaction of lithium derivatives of N,N,N',N'-tetramethyldiamides of arylmethanephosphonic acids (1-Li) with aldehydes 2 is studied. It is found that under certain reaction conditions (THF, 5 hrs at -70°C and then allowing to warm to room temperature) the aldol stage of the reaction is highly stereoselective, only erythro adducts (2-hydroxyphosphonamides) 3, 4 being formed in 47–75% yields. By heating of 3 and 4 in neutral medium the corresponding (Z)-olefins 5, 6 are obtained (yields 64–74%). It is established that an acid catalyzed olefination of 2-hydroxyphosphonamides is also possible, but the reaction is not stereospecific.     

ACTION OF WITTIG‐HORNER REAGENTS ON o-QUINONES

Abstract

When 3,4,5,6-tetrachloro-1,2-benzoquinone (1) was reacted with two molar amounts of triethylphosphonoacetate (I), the corresponding 5,6,7,8-tetrachlorocoumarin-4-carbethoxy-3-diethylphosphonate (4) was obtained. Moreover, phenanthrene-9,10-quinone (2) was converted by reaction of Wittig-Horner reagent (I) into 2,3-dicarbethoxy-phenanthro[9,10-b]dihydrofuran (5) and the dimeric form (6). On the other hand, adducts (7) and (8) were isolated from the reaction of acenaphthenequinone (3) with triethylphosphonoacetate (I). Possible reaction mechanisms are considered and the structure of the new compounds (4), (5, 6) and (7, 8) was confirmed on the basis of the elemental analysis and spectral studies.     

Diels-Alder reaction of fulvenes with N-(3,5-dichlorophenyl)-maleimide

Summary N-(3,5-Dichlorophenyl)-maleimide reacts smoothly with a variety of substituted fulvenes (1) to give onlyendo adducts (3) independent of the nature of fulvene substituent,Lewis acid catalyst, and reaction solvent and temperature. The structure of theDiels-Alder adduct3f was determined by X-ray crystallography. Semi-empirical quantum methods (AM1) were used to rationalize theendo stereoselectivity.Dedicated to Professor Fritz Sauter on the occasion of his 65^th birthday     

Dialkyl (Alkylene) Dithiophosphate Adducts of Anhydrous Stannous Chloride: Synthesis,Characterization, and Biological Activities

Abstract

Dialkyl (alkylene) dithiophosphate adducts of stannous chloride were synthesized by the reaction of anhydrous tin(II) chloride (SnCl₂) and dialkyl (alkylene) dithiophosphoric acid in a 1:1 molar ratio, under anhydrous reaction conditions, below 5 °C in a closed vessel. The newly synthesized adducts were characterized by physicochemical and spectroscopic techniques [FT-IR, NMR (¹H, ³¹P, and ¹¹⁹Sn), and mass spectrometry]. Coordination modalities have indicated a donor–acceptor interaction between sulfur and tin(II) moieties, where tin(II) acts as a Lewis acid. The adducts were found to have significant antibacterial activity against Escherichia coli and Pseudomonas aeruginosa, and antifungal activity against Aspergillus niger and Candida albicans.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Stereoselective Synthesis of Alkyl Z -2-(2-Amino-4-oxo-1,3-thiazol-5(4 H )-yliden)Acetates in Solventless Conditions

Tiourea reacts with dialkyl acetylenedicarboxylates in solventless conditions to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetates in fairly good yields. The stereochemistry of the ethyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetate was established by the use of X-ray single crystal structure analysis. The reaction is completely stereoselective.     

Phosphine-Free Suzuki Cross-Coupling Reaction Using an Efficient and Reusable Pd Catalyst in an Aqueous Medium Under Microwave Irradiation

Abstract

We report here an improved, highly efficient, and general method for the ligand-free Suzuki cross-coupling reaction to the synthesis of biaryls, bipyridyls, thienylpyridine, and allylphenols. Microwave irradiation of (het)aryl halides and (hetaryl, allyl)arylboronic acid N-methyl-iminodiacetic acid (MIDA) ester, using polyurea microencapsulated palladium catalyst (Pd EnCat 30), gave the coupling adducts 1a–x in excellent yields in just 10–18 min.