Mass spectra of ortho substituted 1-phenyl-2-thioureas

The mass spectra of some 1-(o-alkylphenyl)-2-thioureas have been investigated and deuterium labelling shows that the proton lost in the SH? abstraction originates from the α-hydrogens in the o-alkyl group. The intensity of the fragment ion formed by loss of the o-alkyl group increases with the stability of the corresponding alkyl radical.     

Mono and dinuclear palladium complexes of o-alkyl substituted arylphosphane ligands: Solvent-dependent syntheses, NMR-spectroscopic characterization and X-ray crystallographic studies

Palladium(II) chloride complexes of o-alkyl substituted phosphanes were prepared in various solvents with the phosphane ligands o-methylphenyldiphenylphosphane, o-ethylphenyldiphenylphosphane, o-isopropylphenyldiphenylphosphane, o-cyclohexylphenyldiphenylphosphane and o-phenylphenyldiphenylphosphane. The structures of the complexes were characterized by ¹H NMR and ³¹P NMR spectroscopy and elemental analysis. The X-ray structures of PdCl₂(o-methylphenyldiphenylphosphane)₂, PdCl₂(o-isopropylphenyldiphenylphosphane)₂, PdCl₂(o-cyclohexylphenyldiphenylphosphane)₂, PdCl₂(o-phenylphenyldiphenylphosphane)₂, [PdCl₂(o-methylphenyldiphenylphosphane)]₂, [PdCl₂(o-ethylphenyldiphenylphosphane)]₂ and [PdCl₂(o-cyclohexylphenyldiphenylphosphane)]₂ were also determined. We report a systematic, solvent-dependent method to prepare palladium(II) complexes of the aryl phosphines o-methylphenyldiphenylphosphane, o-cyclohexylphenyldiphenylphosphane and o-phenylphenyldiphenylphosphane with a desired nuclearity. We demonstrated that chlorinated solvents promote the formation of dinuclear chlorine-bridged palladium complexes for all five ligands. The ligands preferentially form mononuclear palladium complexes in other solvents where the starting materials are only weakly soluble in the solvent.     

AgOTf and TfOH co-catalyzed isoquinoline synthesis via redox reactions of O-alkyl oximes

Under AgOTf and Brønsted acid co-catalysis, O-alkyl o-alkynylbenzaldoxime derivatives undergo a cyclization-induced N-O cleavage to produce isoquinolines with the simultaneous oxidation of O-alkyl group. This redox-based method provides a general access to diverse isoquinoline-derived heterocycles that are simple, efficient, and tolerant of various functional groups from readily available and hydrolytically stable oxime precursors.     

Novel one-step synthesis of 2-carbonyl/thiocarbonyl isoindolinones and mechanistic disclosure on the rearrangement reaction of o-phthalaldehyde with amide/thioamide analogs

A rearrangement reaction of o-phthalaldehyde with urea/thiourea analogs or amides/thioamides under the catalysis of TMSCl (trimethylchlorosilane) is described, whereby a series of 2-carbonyl isoindolinones and 2-thiocarbonyl isoindolinones are afforded. This is the first time that the N-carbonyl/thiocarbonyl isoindolinones are synthesized in a single step from o-phthalaldehyde. Similar reactions using primary amines also proceed smoothly to give corresponding N-alkyl or N-aryl isoindolinones in this mild catalytic system. The mechanism of this kind of rearrangement is discussed based on new evidences observed from the ESI-MS time-interval monitoring of the full reaction course and deuterium exchange experiments.     

Reaction of o-carboxyphenyl sulfoxides with acetic anhydride : Kinetic studies on the neighboring group effect of ortho-carboxyl group in the oxygen exchange and Pummerer reactions

Kinetic studies on the concurrent oxygen exchange and racemization reactions and Pummerer reaction of o-carboxyphenyl sulfoxides with acetic anhydride were carried out. In the reaction of o-carboxyphenyl phenyl sulfoxide, ortho-carboxyl group was found to enhance the rates of both oxygen exchange and racemization about 180 times, and the rate of racemization was nearly twice that of oxygen exchange. In the reaction of alkyl o-carboxyphenyl sulfoxides, an intramolecular Pummerer reaction took place to give 3,1-benzoxathian-4-one derivatives, and the Pummerer reaction was accelerated about 140 times that of the usual unassisted Pummerer reaction of aryl methyl sulfoxide. A very small deuterium kinetic isotope effect (k_H/k_D = 1.07 with trideuterated-methyl o-carboxyphenyl sulfoxide) and the rate-enhancing effect of α-alkyl group were also noticed. The markedly large rate-enhancement of both oxygen exchange and the Pummerer reactions is undoubtedly caused by the neighboring group participation of carboxyl group in the rate-determining intramolecular acylation of sulfinyl O atom.     

A novel synthesis of 4,5-diaryl-6-arylamino-2,3-benzo-1,3a,6a-triazapentalenes

Treatment of N-alkyl- and N-aryl-imines of 2,3-diaryl- and 2-alkyl-3-aryl-3-(benzotriazol-1-yl)propenals with trifluoroacetic anhydride in THF at room temperature gave 5-alkyl-4-aryl-6-[N-alkyl (and aryl)-N-trifluoroacetyl]amino-2,3-benzo-1,3a,6a-triazapentalenes in moderate to good yields. On heating triazapentalenes having R²=aryl in MeOH at reflux, detrifluoroacetylation of triazapentalene occurred to give title compounds in good yields. However, the same treatment of triazapentalenes having R²=alkyl did not give the corresponding detrifluoroacetylation product. The title compounds and 5-alkyl-4-aryl-6-(N-alkyl-N-trifluoroacetyl)amino-2,3-benzo-1,3a,6a-triazapentalenes were found to be good precursors for the synthesis of 1-(o-aminophenyl)-3-arylamino-4-alkyl (and aryl)-5-arylpyrazoles and 1-(o-aminophenyl)-3-(N-alkyl-N-trifluoroacetyl)amino-4-alkyl (and aryl)-5-arylpyrazoles, respectively.     

Organotin derivatives of (arylazo)benzoic acids : I. Preparation,spectrophotometric titrations and IR spectra

Organotin derivatives of some (arylazo)benzoic acids have been prepared, and investigated by spectrophotometric titration and IR spectroscopy. The organotin (o-arylazo)benzoates are generally penta-coordinated, but those containing a hydroxyl group in the 2-position, e.g., triorganotin o-(2-hydroxy-5-methyl-benzeneazo)benzoate, are hexa-coordinated. The tetracarboxy derivatives contain two different types of tin—carboxylate bonds, as shown by two IR absorptions, at 1700 (ester-like) and 1620 cm^?1 (chelated).     

Nitrile oxide cycloaddition routes to 2-(isoxazolyl)-benzoates and 2-(1,2,4-oxadiazol-3-yl)benzoates

Cycloaddition of aromatic nitrile oxides to methyl o-vinylbenzoate produced methyl 2-(3-aryl-2-isoxazolin-5-yl)benzoates; the isoxazolines were converted to methyl 2-(3-arylisoxazol-5-yl)benzoates. Reaction of the nitrile oxide from o-methoxycarbonylbenzohydroximinoyl chloride ( 11 ) with phenylacetylene, styrenes, and aromatic nitriles resulted in methyl 2-(5-phenylisoxazol-3-yl)benzoate, methyl 2-(5-aryl-2-isoxazolin-3-yl)-benzoates ( 15 ), and methyl 2-(5-aryl-1,2,4-oxadiazol-3-yl)benzoates, respectively. The isoxazolines 15 were converted to the corresponding isoxazoles 16 .     

Photochemical incorporation of protic solvents by open chain olefins

Irradition of methyl styryl sulphoxide dissolved in MeOH, EtOH, or AcOH induces the photochemical polar addition of the solvents to afford the product, PhCH(OR)CH₂SOMe, where R is Me, Et, or Ac. By-products are the corresponding sulphides, PhCH(OR)CH₂SMe, and methyl styryl sulphide. Similar adducts of protic solvents are produced upon irradiation of certain vinylic sulphides, methyl phenethynyl sulphide, as well as appropriately substituted propenylbenzenes including o-anethole, o-anol, and o-propenylaniline in soln.     

Facile synthesis of sulfenyl-substituted isocoumarins,heterocycle-fused pyrones and 3-(inden-1-ylidene)isobenzofuranones by FeCl3-promoted regioselective annulation of o-(1-alkynyl)benzoates and o-(1-alkynyl)heterocyclic carboxylates with disulfides

Reported herein is the FeCl₃-promoted intermolecular sulfoesterification of o-(1-alkynyl)benzoates with disulfides, which provides a convenient and efficient method for synthesis of 4-sulfenylisocoumarins. Various functional groups such as methoxy, halides, ester, cyano and silicon groups in the substrates are tolerated, and heterocycle-fused chalcogenylpyrones are also successfully achieved directly from the corresponding heterocyclic precursors under the same reaction conditions. In addition, starting from diynylbenzoate, this reaction sequence can be combined with a bicyclization step leading to the tetracyclic (E)-3-(2-phenyl-3-phenylchalcogenylinden-1-ylidene)isobenzofuranone frameworks with high regiospecificity and exclusive trans stereoselectivity.     

Temperature dependent product distribution in photolysis of o-alkylphenacyl benzoates

Temperature effect on photochemical reactions of ortho-alkylphenacyl benzoates, one of the recently developed photoremovable protecting groups (PPG), giving indanones (IN) and benzocyclobutenols (CB) was examined. As temperature was lowered, CB was formed preferentially over IN and the amount of IN increased as temperature was elevated. Arrhenius plot of ln(IN/CB) versus 1/T gave a straight line from which Ea_IN–Ea_CB and A_IN/A_CB were obtained. The least sterically hindered 2-methylphenacyl benzoate (1) gave the highest Ea_IN–Ea_CB and A_IN/A_CB among the ortho-alkylphenacyl benzoates tested in this research including 2,4,6-trimethylphenacyl benzoate (2) and 2,4,6-triisopropylphenacyl benzoate (3).     

Reaction of isatin with alkylating agents with acidic methylenes

The reaction of isatin (1) with different alkyl halides 2 and alkaline carbonates in aprotic polar solvents leads mainly to N-alkyl derivatives 3. The use of alkylating agents that have acidic methylenes leads to competitive formation of the corresponding epoxide 5. The formation of 5 is favored by low-polarity solvents at low temperatures and strong bases. Epoxides 5c, d obtained using NaEtOH/EtOH at 0–5 °C are transformed into the corresponding 4-quinolinones 6 at higher temperatures. The use of Ag₂CO₃ allows obtaining compounds 3 as major products, along with varying amounts of labile O-alkyl derivatives 4 and dimerization products.     

Pd/C mediated synthesis of 2-substituted benzo[b]furans/nitrobenzo[b]furans in water

An efficient synthesis of 2-alkyl/aryl substituted benzo[b]furans/nitrobenzo[b]furans in water has been accomplished via Pd/C catalyzed reaction of o-iodophenols with terminal alkynes in the presence of PPh₃, CuI and prolinol. This method can tolerate a variety of functional groups present in the alkynes as well as base labile nitro group in the o-iodophenols. The protocol does not require the use of a phase transfer catalyst or water-soluble phosphine ligands and is free from the use of any organic co-solvent.     

A new electroreductive annellation useful in synthesis of alkaloids

Controlled potential reduction of immonium salts in the presence of bromo esters such as o-bromomethyl benzoates has afforded annellated products. The method is applicable to the synthesis of berbine alkaloids.     

Study of the size and numerical concentration of the free volume of carbon filled HDPE composites by the positron annihilation method

In this paper, the size and numerical concentration of free volume of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples, one with various CB contents in the composites and the other with changing the temperature of HDPE/CB composite containing 25 phr CB. It was found that the important parameters of PALS show their fluctuation around the percolation threshold. The conductivity of HDPE/CB is controlled by CB contribution, and that can be reflected in o-Ps lifetime. The temperature dependence of positron lifetimes reveals that the existence of glass transition temperatures and the size of free volume holes increases when temperature increases above glass transition. The results observed from the second set of samples suggest that positive temperature coefficient is in some way related with free volume expansion. The experiment facts implied that the conductivity of HDPE/CB was related with not only the size of free volume holes but also the number of free volume holes. The Doppler-broadening of HDPE/CB was also investigated.     

Solvent-assisted thiocarboxylation of amines and alcohols with carbon monoxide and sulfur under mild conditions

DMSO or DMF as a solvent strongly accelerated the thiocarboxylation of amines and alcohols with carbon monoxide and sulfur. Under mild conditions (1 atm, 20 °C), this thiocarboxylation of amines assisted by DMSO with carbon monoxide and sulfur has been developed into a practical and convenient synthetic method for S-alkyl thiocarbamates in good to excellent yields, including EPTC, thiobencarb, orbencarb, and molinate (herbicides). DMF also showed the similar solvent effect. NMP slightly decreased the effect for the thiocarboxylation of amines, and the yield of S-alkyl thiocarbamate was lowered in DMAc. Surprisingly, no formation of S-alkyl thiocarbamate was observed at the use of the other solvents, such as THF, hexane, toluene, AcOEt, MeCN, MeOH, and H₂O. The present solvent-assisted thiocarboxylation with carbon monoxide and sulfur could be also applied to a new synthesis of S-alkyl O-alkyl carbonothioates from alcohols under mild conditions (1 atm, 20 °C) in DMF using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene).     

Cyclization reactions of N-acryloyl-2-aminobenzaldehyde derivatives: formal total synthesis of martinellic acid

N-Alkyl acryloylamides derived from o-aminobenzaldehyde derivatives react with N-alkyl glycine derivatives to provide cis-fused pyrrole[3,2-c]quinolones in moderate yield and high diastereoselectivity. These same substrates engage in a tandem Michael-Mannich pathway on treatment with a secondary amine, providing corresponding quinolone derivatives. The elaboration of a pyrroloquinolone derivative via addition of an in situ generated functionalized copper acetylide to an in situ generated iminium ion provided the C2-substituted derivative. Global deprotection and reduction of the alkyne afford the tricyclic triamine core (as the HCl salt) found in martinellic acid.     

Paramagnetische organothallium(III)-verbindungen in lösung : II. Esr-untersuchungen paramagnetischer diphenylthallium(III)-komplexemit o-aminophenolen und o-phenylendiaminen

Diphenylthalliumhydroxide reacts in organic solvents with o-aminophenols and o-phenylenediamines to form paramagnetic species, the ESR spectra of which have been investigated. The reaction has been run using 32 ligands in numerous solvents, therefore the general application of the reaction is proved.The ESR spectra of the solutions show typical hydrogen nitrogen hyperfine structures indicating a NH-analogue semiquinone structure for the ligands. Furthermore a very large splitting due to magnetic coupling of the free electron with ²⁰³Tl- and ²⁰⁵Tl-nuclei is observed. In contrast to the paramagnetic diphenylthallium—semiquinone complexes [1a], the different coupling of ²⁰³Tl- and ²⁰⁵Tl-nuclei could be resolved in several cases.The thallium splitting observed increases from the semiquinone complexes (~10 G) to the aminophenol radicals (~40 G) and reaches a maximum value for the o-phenylenediamine derivatives (~90 G). The corresponding g-values decrease strongly in this direction. Thus a clear distinction of these classes of ligands becomes possible.The experimental thallium coupling constants and the g-factors depend largely on the substituent of the ligand, the solvent and the temperature. These effects are interpreted in terms of solvation phenomena.Based on the sum of the observed effects we assume that in all cases the radicals investigated are ion pairs in which the diphenylthallium cation interacts with a new type of ligand, namely NH-analogue semiquinones.     

Synthesis of Peroxy Bond Containing Acetylene Alcohols,Ethers, and Esters,Derivatives of 2-Octanone

A synthesis was developed of 2,5-dimethyl-2-tert-alkylperoxy-5-lithiumoxy-3-undecynes by treating the corresponding peroxyalkynes with butyllithium followed by reaction of the arising lithium peroxyacetylides with 2-octanone. The lithium peroxyalcoholates undergo hydrolysis with water to furnish peroxy bond containing alcohols. They also react with methyl and ethyl iodides, alkyl and benzyl bromides in the presence of hexamethylphosphoramide to afford the corresponding 2,5-dimethyl-2-tert-alkylperoxy-5-alkyl(benzyl)oxy-3-undecynes, with benzoyl chloride they yield peroxy bond containing benzoates. The thermal stability of the peroxides obtained was estimated by derivatography.     

Über 1-Alkyl-bzw. 1-Aryl-dihydro-6-methyl-2(1H)-pyrimidinthione

The title compounds7 are formed in a general reaction by heating β-isothiocyanoketones3 with primary amines in inert solvents, or by thermal elimination of water from tetrahydro-6-hydroxy-6-methyl-2(1H)-pyrimidinethiones5, also in inert solvents. The 1-alkyl compounds can also be prepared under similar conditions from α,β-unsaturated ketones by reaction with alkylammonium rhodanides. The NMR-spectra show that the 1-substituted dihydro-6-methyl-2(1H)-pyrimidinethiones are in tautomeric equilibrium with the tetrahydro-6-methylene-2(1H)-pyrimidinethiones13. The reactivity of 1-alkyl and 1-aryldihydro-6-methyl-2(1H)-pyrimidinethiones is similar to that of dihydro-4,4,6-trimethyl-2(1H)-pyrimidinethione7 j, although their ring stability is certainly less.