Tandem mass spectrometry and hydrogen/deuterium exchange studies of protonated species of 1,1'-bis(diphenylphosphino)-ferrocene oxidative impurity generated during a Heck reaction

Oxidation of 1,1'-bis(diphenylphosphino)-ferrocene (DPPF) was found to occur when it served as the ligand for Pd(II)(CH3COO)2 in a Heck reaction. This oxidative impurity of DPPF, referred to as DPPF(O), was identified by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) and exact mass measurements. Protonated DPPF(O) exhibited unique fragmentation pathways in the gas phase. Hydrogen/deuterium (H/D) exchange experiments provided important insights into the dissociation mechanisms of protonated DPPF(O), suggesting the existence of isomeric structures of the product ions by retaining or losing a proton (or deuteron) upon collision-induced dissociation (CID). The specific fate of the proton (or deuteron) upon CID is postulated to be dependent on the distance between the exchangeable proton (or deuteron) and the sites of bond cleavage. Density functional theory (DFT) calculations at the B3LYP/LANL2DZ level of theory showed that oxygen in DPPF(O) plays a pivotal role in invoking pi-cation interactions between the p-type lone pair electrons (n pi) in oxygen and the anti-bonding orbital of Fe(II), accounting for the major fragmentation pathways of protonated DPPF(O). Facile formation of organometallic distonic ions in dissociation of protonated DPPF(O), and especially of protonated DPPF, could be useful for further exploration of their chemical properties by gas-phase ion/molecule reactions.     

5-Substituted 2-alkyl- and 2-arylsulfonyliminohexahydro-1,3,5-triazines

A new procedure was developed for the preparation of previously unknown 5-substituted 2-alkyl- and 2-arylsulfonyliminohexahydro-1,3,5-triazines by cyclocondensation of sulfoguanidines with formaldehyde and primary alkyl(aryl)amines.     

Synthesis of chiral 2-alkyl-8-quinolinyl-oxazoline ligands: reversal of enantioselectivity in the asymmetric palladium-catalyzed allylic alkylation

New chiral 2-alkyl-8-quinolinyl-oxazolines were synthesized from 2-alkyl-8-quinolinecarboxylic acids and enantiomerically pure amino alcohols using a convenient procedure. Enantioselective palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate in the presence of 2-alkyl-8-quinolinyl-oxazolines provided an alkylation product with an opposite configuration compared to those obtained from unsubstituted quinolinyl-oxazoline ligands.     

Joint cycloalumination of ethylene and other unsaturated compounds with EtAlCl<Subscript>2</Subscript> in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>. Synthesis of aluminacarbocycles

A procedure has been developed for the selective synthesis of five-membered aluminum-containing heterocycles, 2,3-dialkyl-1-ethylaluminacyclopent-2-enes, 3-alkyl-1-ethylaluminacyclopentanes, 2-alkylidene-1-ethylaluminacyclopentanes, and 3-alkyl-1-ethyl-2-methylidenealuminacyclopentanes, via joint cycloalumination of ethylene and other unsaturated compounds (acetylenes, olefins, and allenes) with EtAlCl₂ in the presence of Cp₂ZrCl₂ as catalyst.     

General route to 2-alkyl-2-butenolactones via the retro-Diels-Alder reaction

Various 2-alkyl-2-butenolactones were simply prepared from cyclopentadiene-maleic anhydride adducts through the retro-Diels-Alder reaction. The procedure was applied for the synthesis of dehydrolappaol A dimethyl ether.     

High yielding microwave-assisted synthesis of 2-(arylmethyl)amino-4-arylamino-6-alkyl-1,3,5-triazines

An efficient and practical procedure was developed to prepare novel 2-(arylmethyl)amino-4-arylamino-6-alkyl-1,3,5-triazines, starting from dicyandiamide and the corresponding arylamines under microwave irradiation and its scope is demonstrated with a number of examples. The valuable feature of this procedure included the short reaction times, high yields, and easy operation.     

Regioselective synthesis of 1-alkyl-5-(indol-3-yl- and -2-yl)pyrrolidin-2-ones from available reagents

The reaction under mild conditions of 1-alkyl-5-hydroxypyrrolidin-2-ones with different indoles having a free 3 position leads exclusively to 1-alkyl-5-(indol-3-yl)pyrrolidin-2-ones but if position 3 is occupied to 1-alkyl-5-(indol-2-yl)pyrrolidin-2-ones.     

New liquid crystalline compounds based on 2-arylthiophenes and 2-(biphenyl-4-yl)thiophenes

A general and versatile route to the 2-alkyl-5-(4'-cyanophenyl)thiophenes was established, involving the condensation of an aryl vinyl ketone with an aldehyde in the presence of a thiazolium catalyst (Stetter procedure) to give a 1,4-diketone which with Lawesson's reagent undergoes ring-closure to give the corresponding arylthiophene. In the final step the exchange of a bromo substituent on the phenyl ring for a cyano group is accomplished by copper(I) cyanide in N,N-dimethylforamamide at reflux. The same sequence afforded 2-alkyl-5-(4'-cyanobiphenylyl)thiophenes. Several of the 1,4-diketones were obtained by conjugate addition of nitroalkanes to aryl vinyl ketones, and treatment of the γ-nitroketones with silica gel-supported potassium permanganate. Three alkyl 5-(4-cyanophenyl)thiophene-2-carboxylates were prepared by condensing β-chlorovinylaldehydes with thioglycolates. The cyanophenylthiophenes exhibited only monotropic phases, but incorporation of an additional phenyl ring provided cyanobiphenylylthiophenes of wide nematic ranges. Transition temperatures of binary mixtures of the cyanophenylthiophenes with 4-n-pentyl-4'-cyanobiphenyl were measured, and extrapolated virtual nematic-isotropic transition temperatures were determined.     

Environmentally friendly synthesis of biaryls: Suzuki reaction of aryl bromides in water at low catalyst loadings

Pd(DPPF)Cl₂ is shown to be an extremely active catalyst for the Suzuki reaction of aryl bromides in water. This green procedure provides biaryls in excellent yields and high turnover numbers (TONs) (TONs up to 870,000 for the reaction of 1-bromo-4-nitrobenzene and phenylboronic acid). A small amount of PEG-2000 also allows the recycling of the palladium catalyst for three times without any significant loss of catalytic activity.     

meso-Aryl-3-alkyl-2-oxachlorins

The formal replacement of a pyrrole moiety of meso-tetraarylporphyrin 1 by an oxazole moiety is described. The key step is the conversion of porpholactones 4 (prepared by a known two-step oxidation procedure from 1) by addition of alkyl Grignard reagent to form meso-tetraaryl-3-alkyl-2-oxachlorins 9 (alkyloxazolochlorins; alkyl = Me, Et, iPr). Hemiacetal 9 can be converted to an acetal, reduced to an ether, or converted to bis-alkyloxazolochlorins 11. The optical properties (UV-visible and fluorescence spectroscopy) are described. The chlorin-like optical properties of the alkyloxazolochlorins are compared to regular chlorins, such as 2,3-dihydroxychlorins and nonalkylated oxazolochlorins made by reduction from porpholactone 4. The conformations of the mono- and bis-alkylated 2-oxachlorins, as determined by single crystal X-ray diffractometry, are essentially planar, thus proving that their optical properties are largely due to their intrinsic electronic properties and not affected by conformational effects. The mono- and bis-3-alkyl-2-oxachlorins are a class of readily prepared and oxidatively stable chlorins.     

A one-step synthesis of 2-Alkyl-5-hydroxychromones and 3-Alkoyl-2-alkyl-5-hydroxychromones

2-Alkyl-5-hydroxychromones (2-alkyl-5-hydroxy-4-oxo-4H-1-benzopyran) and 3-alkoyl-2-alkyl-5-hydroxychromones (3-alkoyl-2-alkyl-5-hydroxy-4-oxo-4H-1-benzopyran) were prepared in one-step and one pot reaction by condensation of 2',6'-dihydroxyacetophenone with an alkoyl chloride in the presence of K2CO3.     

Regioselective synthesis of trifluoromethyl group substituted allylic amines via palladium-catalyzed allylic amination

The palladium-catalyzed regioselective allylic amination of α-trifluoromethylated allyl acetate occurred using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF. The selective formation of the γ-product was attained by Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF.     

Synthesis and hydrodynamic properties of star poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines) based on sulfochlorinated calix[4]arene initiator

New four-arm star poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines) were synthesized using sulfochlorinated calix[4]arene derivative as a multifunctional initiator. Their characteristics were investigated by gel permeation chromatography, light scattering and viscometry. The polymer stars obtained were shown to have well-defined architecture and high intramolecular density.     

Interaction of (z)-4-bromo-1,3-di(2-thienyl)- 2-buten-1-one with amines,synthesis of di(2-thienyl)azolo[<Emphasis Type="Italic">a</Emphasis>]pyridines

(Z)-4-Bromo-1,3-di(2-thienyl)-2-buten-1-one was obtained by the bromination of 1,3-di(2-thienyl)-2-buten-1-one by NBS in anhydrous CCl₄. The starting butanone was obtained by the condensation of 1-(2-thienyl)-1-ethanone by the action of SOCl₂. The reaction of (Z)-4-bromo-1,3-di(2-thienyl)-2-buten-1-one with tertiary amines such as Et₃N, pyridine, 1-alkyl-1,3-diazole, 1-alkylbenzimidazole, and 1-alkyl-1,2,4-triazole leads to quaternary salts. The azolium salts cyclize by the action of base to give di(2-thienyl)azolo[a]pyridinium derivatives. 3-Methyl-6,8-di(2-thienyl)[1,3]thiazolo[3,2-a]pyridin-4-ium and 2,4-di(2-thienyl)pyrido[2,1-b]benzothiazol-10-ium bromides were obtained by the same procedure but without separating the intermediate quaternary salts.     

Synthesis and Properties of 2-Alkyl-1-(2-aminoethyl)pyrroles

3-Chloropropenyl alkyl ketones or 2-methoxy-3-chloropropyl alkyl ketones in reaction withethylenediamine furnish previously unknown 2-alkyl-1-(2-aminoethyl) pyrroles. Their reaction with 2'2'-dichlorodiethyl ether gave rise to 2-alkyl-1-(2-morpholinoethyl)pyrroles, with anhydrides ofdicarboxylic acids the corresponding amidoacids and imides of dicarboxylic acids were obtained.     

Halogenation of 2-alkyl-2-azabicycloalkenes as a method for the synthesis of stable aziridinium salts of a new class

Addition of bromine and potassium dihaloiodates(i) to 2-alkyl-2-azabicyclo[2.2.1]hept-5-enes and 2-alkyl-2-azabicyclo[2.2.2]oct-5-enes affords quaternary ammonium salts containing the aziridine ring and the polyhalide anion. The possibility of using these salts for the synthesis of 6-substituted 2-alkyl-2-azabicyclo[2.2.1]heptanes has been shown.     

The preparation of 5-(2-bromoethyl)-2-iminooxazolidines via the von braun cyanogen bromide reaction

The reaction of certain 1-alkyl-3-pyrrolidinols with cyanogen bromide in ether solution produced 3-alkyl-5-(2-bromoethyl)-2-iminooxazolidines. 5-(2-Bromoethyl)-2-ethyl-2-imino-5-phenyloxazolidine was tested for and found devoid of anorectic activity.     

Three-component synthesis of methyl 6-alkyl-3-cyano-2-halopyridine-4-carboxylates

A procedure has been developed for the synthesis of methyl 6-alkyl-3-cyano-2-halopyridine-4-carboxylate by three-component reaction of 4-oxoalkane-1,1,2,2-tetracarbonitriles with hydrogen halides in methanol.     

Regioselective synthesis of 5-alkylsalicylates, 5-alkyl-2-hydroxy-acetophenones, and 5-alkyl-2-hydroxy-benzophenones by [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 2-alkyl-1,1,3,3-tetraethoxypropanes

A variety of 5-alkylsalicylates, 5-alkyl-2-hydroxy-acetophenones, and 5-alkyl-2-hydroxy-benzophenones was regioselectively prepared by TiCl4 mediated formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 2-alkyl-1,1,3,3-tetraethoxypropanes.     

Optically Active Alkylvinylpyridines: Synthesis of (+)-(S)-6-(1-Methylpropyl)-2-Vinylpyridine

A generalizable procedure for the preparation of optically active 6-alkyl-2-vinylpyridines from chiral 2-alkylpyridines without loss of optical purity is reported.