System In THF Research Articles

Unexpected Rearrangement of Dilithiated Isoindoline-1,3-diols into 3-Aminoindan-1-ones via N-Lithioaminoarylcarbenes: A Combined Synthetic and Computational Study.

The reaction of 2-aryl-3-hydroxyisoindolin-1-ones with the s-BuLi·TMEDA system in THF at -78 °C, affording a series of diastereomeric 3-aminoindan-1-ones via a novel rearrangement of the isoindolinone scaffold, is reported. It is proposed that α-elimination of LiOH from the transient N,O-dilithiated hemiaminal carbenoids leads to the formation of singlet carbenes followed by their trapping via an intramolecular C-H insertion. An alternative explanation based on an intramolecular Mannich reaction seem much less probable. A mechanistic-type study that combines spectroscopic data of the products and calculation results, with a special focus on the diverse lithiated intermediates that are most likely to engage in the title process (particularly those with internal Li bonds), is presented. The MP2 approach, including the NPA and QTAIM data, provided insight into structures and properties of all these species. Two reaction routes A and B appeared to be possible for the postulated carbene mechanism. An unusual metamorphosis of the CCN atom triad, from a near sp 1-azaallene-type in more stable noncarbene Li enolates to a roughly sp2 type in their carbene keto tautomers, is recognized in one of these pathways (route B). Dominant forms of resonance structures for the aforementioned tautomeric systems that have seven-membered quasi rings stabilized by Li+ ions bridging the N and carbonyl O atoms are indicated. Large computational difficulties arising from a huge impact of internal Li+ complexation on conformational preferences and electronic properties of carbonyl group-bearing lithium derivatives are also discussed. The new γ-keto carbene species under study belong to a subclass of acyclic aminoarylcarbenes.

Well-Defined Poly(α-amino-δ-valerolactone) via Living Ring-Opening Polymerization

This article demonstrates the synthesis of a new kind of cationic poly(δ-valerolactone) with primary amino groups at α-positions (poly(α-NH2-VL)) via ring-opening polymerization (ROP) of α-NHBoc-valerolactone (α-NHB-VL) followed by a simple deprotection reaction. The ROP of α-NHB-VL using benzyl alcohol as an initiator and DBU/TU (1,8-diazabicyclo[5.4.0]undec-7-ene/thiourea) as a catalytic system in THF at room temperature afforded poly(α-NHB-VL) with narrow molecular weight distribution. The 1H NMR and MALDI-TOF MS analysis of poly(α-NHB-VL) indicated that each polymeric chain was capped by the initiator. Kinetic experiments confirmed the living nature of the DBU/TU-catalyzed ROP of α-NHB-VL in THF. The copolymerization result indicated that the polymerization activity of α-NHB-VL is comparable to that of e-caprolactone (CL) and VL. In addition, block copolymers containing poly(α-NHB-VL) were successfully synthesized regardless of whether hydrophilic PEG or hydrophobic PCL was used as the macroinitiator....

Convenient Reductive Amination of Aldehydes by NaBH4/Cation Exchange Resin

Different secondary amines have been synthesized by reductive amination a variety of aldehydes and anilines with NaBH4/DOWEX(R)50WX8 as reducing system in THF at room temperature in high to excellent yields of products (85-93%).

Oxidative Desulfurization of Coal Tar Pitch Using a Urea–Hydrogen Peroxide Complex/Carboxylic Anhydride System in THF

Abstract Oxidative desulfurization of coal tar pitch (CTP) using a urea–hydrogen peroxide complex with a carboxylic anhydride in THF was investigated. The sulfur content in CTP was reduced by more than 15% through the process.

Convenient high-pressure syntheses of [PtX3(C2H4)]− (X = Cl, Br) salts with a variety of organic cations from PtX2

Reaction between PtX2 (X = Cl or Br) with an equimolar amount of the appropriate [Cat]+X− in toluene in an autoclave under 25 bars of C2H4 yields the corresponding [Cat][PtX3(C2H4)] in moderate to excellent isolated yields and high purity (X = Cl, Cat = nBu4P; X = Br, Cat = nBu4P, Ph4P, nBu4N). The same reaction does not yield any olefin complex if X = I and no reaction also occurs for the PtBr2 + KBr system in water, THF, acetone or toluene.

Synthesis of amides from imines using Et3SiH/Zn system

A simple and efficient approach for the synthesis of amides by the reaction of imines and acyl chlorides in the presence of Et3SiH/Zn system in THF at ambient temperature is reported. Mild reaction conditions, good yields of products, short reaction time and operational simplicity are the advantages of this procedure. Copyright © 2012 John Wiley & Sons, Ltd.

Copper mediated defluorinative allylic alkylation of difluorohomoallyl alcohol derivatives directed to an efficient synthetic method for ( Z)-fluoroalkene dipeptide isosteres

Difluoroallylation of optically pure O-silylated ( S)-2-methyl-3-hydroxypropanal 10a with bromodifluoropropene mediated by indium provided the corresponding difluorohomoallyl alcohol 11a with low diastereoselectivity, but without a decrease in optical purity. Defluorinative allylic alkylation of each diastereomer of the difluorohomoallyl alcohol efficiently proceeded by the reaction with trialkylaluminium and Cu(I) system or Grignard reagent and a catalytic amount of CuI system in THF to give the fluorine-substituted allylic alcohol 12 in an high yield and in an excellent Z selective manner. Subsequent imidate Claisen rearrangement of the allylic alcohol 12 proceeded with a complete 1,3-chirality transfer to give the fluoroalkene dipeptide isostere structure 14 after the final conversion of the primary alcohol 20 into the carboxylic acid form.

An Improved Synthesis of Symmetrical Diselenides from Aromatic Aldehydes

An improved method for the synthesis of symmetrical diselenides is described. Reductive selenation of aromatic aldehydes with Se/CO/H2O/Et3N system in THF gave the corresponding aromatic diselenides in good yields.

Study of magnetic field effect on Py-DMA exciplex luminescence in THF–DMF binary solvents: Evidence of multiple exciplex formation at higher bulk dielectric constant

Magnetic field effects (MFE) on pyrene-DMA (N,N-dimethylaniline) exciplex system in THF–DMF binary solvents of varying bulk dielectric constant ( ε) has been studied. The MFE has been wavelength resolved over the emission band of the exciplex. The data indicates formation of two types of exciplexes at higher bulk value of ε. At lower value of ε ( ε < 9) essentially there is a single type of exciplex which is supported by the wavelength resolved MFE and life-time ( τ) measurements. However, at higher value of ε ( ε > 15) when the solvent reorganization energy is more prominent; the wavelength resolved MFE and life-time studies show evidence of two types of exciplexes.

Terphenyl based ‘Turn On’ fluorescent sensor for mercury

New terphenyl-based derivative 4 with pyrene as a fluorophore has been synthesized and examined for its cation recognition abilities toward various cations by NMR and fluorescence spectroscopy. The results show that it has very high binding affinity (log β = 5.12) and selectivity for mercury. A fluorescence enhancement of 375% was observed for the 4-Hg 2+ system in THF. A Hg 2+ selective electrode (ISE) was also formed which showed excellent selectivity over all the other cations tested. The lower limit of detection is 2.1 × 10 −6 M.

A Novel Efficient Four- and Five-Component, One-Pot Synthesis of 4-Semicarbazonoalkyl-2-Naphthols

One-pot, multicomponent coupling reaction of two or three molecules of aldehydes with 2-naphthols and semicarbazide hydrochloride is described for the preparation of 4-semicarbazonoalkyl-2-naphthols using PTSA/NaOAc as an efficient catalyst system in THF at room temperature or solvent-free conditions at elevated temperature.

ChemInform Abstract: Reductive Amination of Aldehydes and Ketones in a Heterogeneous System in THF and under Solvent‐Free Conditions Using Sodium Borohydride‐Silica Phosphoric Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reductive Amination of Aldehydes and Ketones in a Heterogeneous System in THF and under Solvent-Free Conditions Using Sodium Borohydride-Silica Phosphoric Acid

A chemoselective, fast, efficient, and high yielding method for the preparation of amines by reductive amination of aldehydes and ketones using sodium borohydride in the presence of silica phosphoric acid in THF and under solvent-free conditions at room temperature is described.

Facile Synthesis of E‐Diiodoalkenes: H2O2‐Activated Reaction of Alkynes with Iodine

Hydrogen peroxide was found to activate iodine in the addition reaction with triple bonds. A facile and technologically straightforward procedure was developed for the synthesis of E‐diiodoalkenes based on the reaction of alkynes with an I2–H2O2 system in THF. Selective iodination of terminal and internal alkynes containing electron‐donating and electron‐withdrawing substituents afforded 16 E‐diiodoalkenes in yields up to 89%.

Mild and Convenient Method for Reduction of Carbonyl Compounds with the NaBH4/Charcoal System in Wet THF.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Mild and Convenient Method for Reduction of Carbonyl Compounds with the NaBH4/Charcoal System in Wet THF

The NaBH4/C (charcoal) system reduces a variety of carbonyl compounds such as aldehydes, ketones, acyloins and α-diketones to their corresponding alcohols in high to excellent yields. Reduction reactions were carried out in wet THF at r. t. In addition, regioselective 1,2-reduction of α,β - unsaturated aldehydes and ketones was achieved perfectly with this reducing system. By decreasing the amount of aprotic solvent, all reductions took place fast and efficiently under solid-gel condition

Synthesis of Quinoline N‐Oxides from the Baylis—Hillman Adducts of 2‐Nitrobenzaldehydes: Conjugate Addition of Nitroso Intermediate.

The Baylis-Hillman reaction is a useful carbon-carbon bond-forming method from activated vinyls and carbonyl compounds. Chemical transformation of the BaylisHillman adducts or their derivatives into useful heterocyclic compounds has been studied recently by us and other groups. Especially, conversion of the Baylis-Hillman adducts derived from 2-nitrobenzaldehydes into quinoline skeleton is a useful entry for the quinoline chemistry. Kaye and co-workers have reported the synthesis of quinoline skeleton from the Baylis-Hillman adducts. We have also reported the synthesis of 4-hydroxyquinoline Noxides from the Baylis-Hillman adducts of 2-nitrobenzaldehydes. As a continuing study, we examined the synthesis of quinoline N-oxides 2 by reduction of the nitro functionality of the Baylis-Hillman adducts 1 into nitroso group followed by dehydrative cyclization strategy. Among the various examined reduction conditions, the use of zinc and ammonium chloride system in aqueous THF was found to be effective. The nitro group is readily converted to a series of functions of various degrees of reduction: very exceptionally to a nitroso group, more often to a hydroxylamino group and most frequently to the amino group. Nitroso compounds are usually not obtained directly but rather by reoxidation of hydroxylamino compounds, which can be prepared from nitro compounds by zinc and aqueous ammonium chloride. Moreover there have been few instances in which nitroso compounds have been isolated as intermediates in reductions of nitro compounds. In some instances the nitroso nitrogen behaves as a nucleophile with formaldehyde, glyoxylic acid and pyruvic acid. Only one example of the conjugate addition of arylnitroso compound to the conjugated azoalkene system was known to the best of our knowledge. The reaction of the Baylis-Hillman adduct 1a and zinc (2.0 equiv) and ammonium chloride (2.0 equiv) in aqueous THF at 60-70 C gave the quinoline N-oxide 2a in 49% isolated yield (Scheme 1) together with many intractable side products. In the reaction, quenching of the unstable nitroso intermediate (I) occurred before further reduction to a hydroxylamine stage due to the facile intramolecular Michael addition process. This might be the first example of conjugate addition of the nitroso intermediate to the Michael acceptor in an intramolecular fashion as mentioned Scheme 1

Mild and Efficient Deoxygenation of Epoxides with Bis(cyclopentadienyl)titanium(IV) Dichloride-Indium System

The deoxygenation of epoxides to olefins is an important synthetic transformation in organic chemistry. Since the combination epoxidation/deoxygenation would provide a useful protection/deprotection sequence for the multiple bond, a variety of methods have been devised to accomplish the transformation. These include FeCl3/n-BuLi, 2 NaOH/ n-Bu4NBr, 3 Mo(CO)6, 4 SmI2, 5 Cp2TiCl2/Mg, 6 and dimethyl diazomalonate. However, many of these remain incompatible with other functional groups in the organic substrates and require expensive reagents and harsh reaction conditions. There still exist a need for the development of new efficient and readily available reagents for this conversion. The chemical reactivity of Cp2TiCl2/M system (M = Zn, Al, Mg, Sm) has been the subject of considerable interest and the reducing ability of these systems has been extensively studied. Because of the close resemblance of indium to magnesium and zinc in several respects, including first ionization potential, we considered that Cp2TiCl2/In system can be an efficient reagent for the deoxygenation of epoxides to olefins. Thus we have investigated the reactions of Cp2TiCl2/In system with various epoxides and found that epoxides can be rapidly deoxygenated to give the corresponding olefins in good to excellent yields (eq. 1). Herein we describe a new and efficient deoxygenation of a variety of epoxides to olefins with Cp2TiCl2/In system in THF under mild conditions. Due to the unique features of high

Synthesis of Quinoline N-Oxides from the Baylis-Hillman Adducts of 2-Nitrobenzaldehydes: Conjugate Addition of Nitroso Intermediate

The Baylis-Hillman reaction is a useful carbon-carbon bond-forming method from activated vinyls and carbonyl compounds. Chemical transformation of the BaylisHillman adducts or their derivatives into useful heterocyclic compounds has been studied recently by us and other groups. Especially, conversion of the Baylis-Hillman adducts derived from 2-nitrobenzaldehydes into quinoline skeleton is a useful entry for the quinoline chemistry. Kaye and co-workers have reported the synthesis of quinoline skeleton from the Baylis-Hillman adducts. We have also reported the synthesis of 4-hydroxyquinoline Noxides from the Baylis-Hillman adducts of 2-nitrobenzaldehydes. As a continuing study, we examined the synthesis of quinoline N-oxides 2 by reduction of the nitro functionality of the Baylis-Hillman adducts 1 into nitroso group followed by dehydrative cyclization strategy. Among the various examined reduction conditions, the use of zinc and ammonium chloride system in aqueous THF was found to be effective. The nitro group is readily converted to a series of functions of various degrees of reduction: very exceptionally to a nitroso group, more often to a hydroxylamino group and most frequently to the amino group. Nitroso compounds are usually not obtained directly but rather by reoxidation of hydroxylamino compounds, which can be prepared from nitro compounds by zinc and aqueous ammonium chloride. Moreover there have been few instances in which nitroso compounds have been isolated as intermediates in reductions of nitro compounds. In some instances the nitroso nitrogen behaves as a nucleophile with formaldehyde, glyoxylic acid and pyruvic acid. Only one example of the conjugate addition of arylnitroso compound to the conjugated azoalkene system was known to the best of our knowledge. The reaction of the Baylis-Hillman adduct 1a and zinc (2.0 equiv) and ammonium chloride (2.0 equiv) in aqueous THF at 60-70 C gave the quinoline N-oxide 2a in 49% isolated yield (Scheme 1) together with many intractable side products. In the reaction, quenching of the unstable nitroso intermediate (I) occurred before further reduction to a hydroxylamine stage due to the facile intramolecular Michael addition process. This might be the first example of conjugate addition of the nitroso intermediate to the Michael acceptor in an intramolecular fashion as mentioned Scheme 1

Analysis of the Effects of Protic, Aprotic, and Multi-Component Solvents on the Fluorescence Emission of Naphthalene and its Exciplex with Triethylamine

The emission spectra of naphthalene (NP)-triethylamine (TEA) systems were measured under steady-state illumination conditions in some protic and aprotic solvent-tetrahydrofuran (THF) mixtures. The fluorescence spectrum of the NP-TEA system in THF could be separated into two component bands (band A at 329 nm (fluorescence of NP) and band B at 468 nm (emission from an intermolecular exciplex)). The intensities of bands A and B decreased with increasing solvent polarity. The intensity of band B also decreased owing to the hydrogen-bonding interaction between TEA and protic solvents, but in this case the intensity of band A increased. The decrease in the intensity of band A with increasing solvent polarity is considered to be caused by the enhanced formation of an ion-pair parallel to the formation of an exciplex with increasing solvent polarity. The decrease in the intensity of band B is considered to be caused by the enhanced formation of ion-pair both parallel to and through the formation of the exciplex. The increase in the intensity of band A and the decrease in that of band B upon the addition of protic solvents is caused by the decrease in the concentration of free TEA. Acetonitrile only has a polar effect and trichloroacetic acid only has a hydrogen-bonding (protonation) effect, while alcohols have both the effects.