Electron impact mass spectrometry of substituted benzyl(1-allylcycloalkyl)amines and their cyclization products

Electron impact mass spectra have been measured for benzyl(1-allylcycloalkyl)amines and α-phenylethyl(1-allylcycloalkyl)amines and for the spiro(benzo-2-azepine-3,1′-cycloalkanes) produced by their cyclization.     

Synthesis of chiral 1,3-dihydroisobenzofurans (phthalans) containing functional substituents in the 1-position

Chiral 3-methyl-1,3-dihydroisobenzofurans (phthalans) having a carbonyl or α-hydroxybenzyl group in position 1 were synthesized by cyclization of the corresponding trimethyl[(S)-1-phenylethyl]ammonium iodides. The configuration of the chiral centers in the products was determined by X-ray analysis.     

Peroxy radical reactivities in the cooxidation of ethylbenzene and substituted 3-phenylindans

The rate constants of peroxy radical recombination in the oxidation of 1-methyl-3-phenylindan, 1,3-dimethyl-3-phenylindan, and 1,1-dimethyl-3-phenylindan were measured using the nonstationary-state technique. A cooxidation method was applied to obtain the reactivities of these compounds with respect to α-phenylethyl peroxy radicals.     

Photoionization of the C-1?C-4 monosubstituted alkyl benzenes: Thermochemistry of [C7H7]+ and [C8H9]+ formation

The appearance energies for the [C₇H₇]⁺ and [C₈H₉]⁺ fragment ions produced in the fragmentation of the C-1? C-4 monosubstituted alkyl benzenes have been measured by photon impact. The mean heat of formation calculated for [C₇H₇]⁺ is 205.3 ± 1.9 kcal mol^?1 which is consistent with a threshold tropylium structure. For [C₈H₉]⁺ the mean heat of formation is calculated to be 199.2 ± 1.3 kcal mol^?1 which can be equated with either a methyl tropylium or α-phenylethyl structure at threshold. Some evidence is provided for the existence of the α-phenylethyl ion.     

Synthesis and reactions of α-fluoro-α-amino amides

N-((S)-1-Phenylethyl)halofluoroethanamides have been investigated as precursors to N-protected α-fluoro-α-amino amides by nucleophilic displacement of halide with nitrogen nucleophiles such as potassium phthalimide, sodium succinimide, sodium glutarimide, trimethylamine and sodium azide. With single diastereoisomers of the iodofluoroethanamide, clean inversion of configuration occurs at room temperature, but subsequent epimerisation may occur as a result of the liberated iodide. The α-fluoro-α-amino amides made underwent a wide variety of reactions depending on conditions, but in many cases the carbon-fluorine bond was compromised. However, reacting trimethylamine and N-((S)-1-phenylethyl)iodofluoroethanamide gave the corresponding α-fluorobetaine amide, and subsequent acidic hydrolysis led to α-fluorobetaine as the first example of an ‘unprotected’ α-fluoroamino acid.     

Mechanisms of elimination reactions—XXVII: The reactions of 1-arylethyldimethylsulfonium bromides with sodium ethoxide in ethanol

Treatment of 1-phenylethyldimethylsulfonium bromide 1 with sodium ethoxide in ethanol at 35° affords four products by five reaction paths: styrene 2 by E2 and α'-β mechanisms, ethyl 1-phenylethyl ether 3 and methyl 1-phenylethyl sulfide 4 by the S_N2 mechanism, and methyl o-ethylbenzyl sulfide 5 by a Sommelet-Hauser rearrangement. Isotope effects of 5.9 and 3.5 for E2 and α'-β reactions were estimated by comparing the deuterium content of methyl sulfide from β-d₃, and α-d₇ (all α-positions exchanged) sulfonium salt. Product analyses on products from the unsubstituted, p-methyl, p-fluoro, p-bromo and m-chloro sulfonium salts were combined with overall rates to calculate partial rates for the formation of each product. These partial rates were fitted to the Hammett equation to give values for each product as follows: 2, 0.95±0.19; 3, ?0.63±0.41; 4, 0.95±0.11; 5, 4.84±0.38. The mechanistic implications of the results are discussed.     

First asymmetric synthesis of a C2-symmetric 2-endo,6-endo-disubstituted bispidine

The enantioselective synthesis of a C₂-symmetric 2-endo,6-endo-disubstituted bispidine (3,7-diazabicyclo[3.3.1]nonane) has been accomplished for the first time. The key step was a Michael addition of the protected β-amino ester methyl (R)-3-{N-benzyl-N-[(S)-1-phenylethyl]amino}-3-phenylpropionate to its α-methylene derivative delivering an anti,anti-configured α,α′-methylene-bridged bis(β-amino ester) as the major diastereomer. Deprotection, reduction and cyclisation furnished (1R,2R,5R,6R)-2,6-diphenyl-3,7-bis((S)-1-phenylethyl)-3,7-diazabicyclo[3.3.1]nonane in six steps and 15% overall yield.     

Synthesis, optical resolution and absolute configuration of inherently chiral calixarene carboxylic acids

Both enantiomers of inherently chiral calixarene carboxylic acids with ABCD substitution patterns have been prepared by the benzoylation of 25-propoxy-27-(R)-N-(α-phenylethyl)amidomethyloxycalix[4]arene followed by resolution of the diastereomers formed, monobromination of them and removal of the benzoyl and α-phenylethylamide auxiliary groups. The absolute configuration of the calixarenes obtained has been established by X-ray analysis. Preliminary study of the chiral recognition properties of calixarene carboxylic acid was performed.     

Studies on model oligosulfides to understand polysulfide polymers

1-bromo-1-phenylethane was reacted with aqueous sodium disulfide or sodium tetrasulfide to form the 1-phenylethyl polysulfides of sulfur rank 2 or 4 respectively. The distribution of the 1-phenylethyl polysulfides thus formed was studied using¹H NMR and GC-MS analysis. Apart from 1-phenylethyl disulfide and 1-phenylethyl tetrasulfide being produced in large amounts when aqueous sodium disulfide and sodium tetrasulfide were used respectively, the formation of 1-phenylethyl monosulfide in the former case and both mono and disulfide in the latter case, in minor amounts, is also observed. Also, it was found that the undetection of the molecular ion peaks of 1-phenylethyl polysulfides having rank above 2 is due to their thermal decomposition to elemental sulfur, 1-phenylethyl mono and disulfide, under the heating conditions employed for GC-MS analysis.     

Chemical ionization induced competing and consecutive heterolytic ring cleavages in the mass spectra of substituted tetrahydro-1,3,2-oxazaphosphorin-2-oxides

The chemical ionization mass spectra of some substituted heterocyclic systems, viz. tetrahydro-1,3,2-oxazaphosphorin-2-oxides, reveal polar cycloreversion reactions. The zwitterion intermediate formed by the heterolysis of the C? O bond undergoes stepwise clean heterolysis further resulting in the expulsion of the potential nucleophilic and electrophilic groups. The competitive and consecutive heterolysis of the ring bonds leads to the formation of the protonated phenylimine ions. Competing with heterolysis, elimination reactions involving hydrogen transfer leading to the formation of α-phenylethyl ions are also observed. The chemical ionization mass spectrometry of the heterocyclic system shows many features of the Grob type of fragmentation mechanism.     

Preconcentration of gold,silver, palladium,platinum, and ruthenium with organophosphorus extractants

Extraction of noble metals in acid media with new tertiary phosphines and phosphine chalcogenides was examined. Tristyrylphosphine, tristyrylphosphine sulfide tris(2-phenylethyl)phosphine oxide, tris-(2-phenylethyl)phosphine sulfide, bis(2-phenylethyl)[2-(propylthio)ethyl]phosphine oxide, bis(2-phenylethyl)-[2-(butylthio)ethyl]phosphine oxide, and tris[2-(butylthio)ethyl]phosphine oxide were used as extractants. The suitability of the extractants for determination of Au, Ag, and Pd in rock and ore samples was elucidated.     

Enantioselective Resolution of (±)-l-Phenylethyl Acetate by Using the Whole Cells of Deep-sea Bacterium Bacillus sp. DL-2

Bacillus sp. DL-2 was isolated from the deep sea of the Western Pacific and further utilized as novel biocatalysts to efficiently asymmetrically hydrolyze (±)-1-phenylethyl acetate. After the optimization of hydrolytic reactions, chiral chemicals (R)1-phenylethanol and (S)-l-phenylethyl acetate were obtained with high optical purities (96% and 99.8%, respectively). Our research is about the asymmeric hydrolysis of (±)-1-phenylethyl acetate using whole-cell biocatalysts. In addition, the optical purity of (S)-l-phenylethyl acetate generated through the kinetic resolution of (±)-1-phenylethyl acetate using the whole-cells of Bacillus sp. DL-2 was the highest report so far. Using the whole cells of deep sea bacterium Bacillus sp. DL-2 as the biocatalysts is an enviromnentally friendly method and will play critical roles in industrial asymmetric synthesis.     

Four new 2-(2-phenylethyl)chromone derivatives from withered wood of Aquilaria sinensis

Four new chromone derivatives, 5-hydroxy-6-methoxy-2-(2-phenylethyl)chromone (1), 6-hydroxy-2-(2-hydroxy-2-phenylethyl)chromone (2), 8-chloro-2-(2-phenylethyl)-5,6,7-trihydroxy-5,6,7,8-tetrahydrochromone (3), 6,7-dihydroxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone (4) were isolated from the MeOH extract of withered wood of Aquilaria sinensis, together with seven known constituents of agarwood.     

Diastereomeric separation of α-amino acid derivatives using a chiral carbodiimide

N,N′-Bis[(S)-1-phenylethyl]carbodiimide (1) was found to be an efficient chiral derivatizing agent for the diastereomeric separation of 2-N-benzyloxycarbonylamino acids (2). Diastereomeric acylureas prepared from 1 and 2 showed a large chromatographic selectivity (α). Their capacity factors and selectivity depend on the carbon chain length of the α-alkyl substituents of acylureas.     

Synthesis and structure of bis(2-phenylethyl) phosphine selenide

Bis(2-phenylethyl)phosphine selenide was obtained with 86% yield from bis(2-phenylethyl)phosphine and selenium. XRD, IR, UV, and multinuclear NMR spectroscopic studies revealed that the phosphorus atom in the bis(2-phenylethyl)phosphine selenide molecule is four-coordinated irrespective of the phase state (crystals or solution).     

Microwave Induced Reaction of H-Dimethylphosphonate with Styrene Oxide

Microwave catalyzed reaction of a neat mixture of styrene oxide and H-dimethylphosphonate furnished dimethyl methylphosphonate, trimethylphosphate, phenylacetaldehyde, 1-methoxy-2-phenylethanol, 1-phenylethleneglycol, cis- and trans-1,3-diphenylcyclobutanes, hydrogen 1-(2-phenylethyl)methylphosphinate, (1-phenylethyl)dimethylphosphonate, and (1-phenylethyl)dimethylphosphonate via free radical processes.     

Oxidative Addition of Dimethyl Malonate to Styrenes Mediated by Cerium(Iv) Ammonium Nitrate: Some Novel Observations

The oxidative addition of dimethyl malonate to ring substituted styrenes leads to the formation of substituted dimethyl (2-oxo-2-phenylethyl) malonate and methyl 2-oxo-5-phenyltetrahydrofuran-3-carboxylate along with small amounts of substituted dimethyl [2-(nitrooxy)-2-phenylethyl] malonate and dimethyl 2-methoxy-2-phenylethyl) malonate. A tentative mechanism which supports the formation of these products is also presented.     

Six new 2-(2-phenylethyl)chromones from Agarwood

Six new chromones, 6-methoxy-2-[2-(3-methoxy-4-hydroxyphenyl)ethyllchromone (2), 6,8-dihydroxy-2-(2-phenylethyl)chromone (3), 6-hydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (4), 6-hydroxy-2-[2-(2-hydroxyphenyl)ethyl]chromone (5), 7-hydroxy-2-(2-phenylethyl)chromone (6), and 6-hydroxy-7-methoxy-2-(2-phenylethyl)chromone (7) were isolated from the ether extract of agarwood in addition to a known compound, 2-(2-phenylethyl)chromone or flidersiachromone (1). Their structures were determined by spectroscopic methods including UV, IR, and NMR spectral data and comparisons with the calculated values using the hydroxyl and methoxyl substituent increments of the chromone ring.     

Relative stabilities of the methyltropylium and α-phenylethyl cations

Metastable decomposition of ethylbenzene molecular ions should yield [C₈H₉]⁺ ions of nearly threshold energies. Mass spectral data from collisionally activated dissociation of these ions show them to be mainly the methyltropylium (a) isomer, which is also that formed from 7-methylcycloheptatriene and isopropylbenzene. Combined with the threshold photoionization studies of McLoughlin, Morrison and Traeger, this establishes a as the most stable [C₈H₉]⁺ isomer. This is more stable than the α-phenylethyl isomer (b), which can be formed from α-bromoethylbenzene molecular ions; higher energy b ions appear to isomerize to a.     

Beitrag zum Mechanismus der stossinduzierten Fragmentierungen von quaternären Stickstoffverbindungen. 2. Mitteilung über stossinduzierte Fragmentierungen von felddesorbierten Kationen

Mechanistic studies on the collision-induced fragmentations of quaternary ammonium ions The collision-induced fragmentation behaviour of field desorbed quarternary ammonium ions has been investigated. A main reaction of these ions is the cleavage of the N? C bond accompanied by hydrogen rearrangement, i.e. alkane loss from the tetraalkyl substituted ammonium ions of the iodides 1, 2 and 3 , respectively, Deuterium labelling indicates that the hydrogen transfer to the leaving group occurs to the extent of about 80% from the α-position and about 20% from the other positions of an alkyl group. Pronounced heterolytic cleavage of the N? C bond is observed in the benzyl substituted ammonium ion of 4 . The β-phenylethyl substituted ammonium ion of 5 shows a homobenzylic heterolysis, possibly yielding the phenonium ion j.