A general synthetic route to 3,5-substituted boron dipyrromethenes: applications and properties

An efficient protocol for the direct synthesis of 3-substituted and 3,5-disubstituted BODIPY derivatives via electrophilic attack with NBS was developed. Various substituents like ethers, sugar, hydroxyl, thiophene, sulfur, azide, tertiary amines, alkyne, vinyl, or phosphonate groups were obtained in moderate to excellent yields. The amine-substituted derivatives display unusual spectroscopic and electrochemical properties which were analyzed in solution in the presence of HCl. The diethylamino-substituted derivative has a proton association constant of log β = 4.7, and the disubstituted derivative has two association constants of log β = 6.2 and 12.1 in ethanol. In both cases, the quenching of the fluorescence is explained by photoinduced electron transfer from the tertiary amine to the Bodipy excited state.     

Synthesis and properties of amino acid esters of hydroxypropyl cellulose

The amino acid esters of hydroxypropyl cellulose (HPC) [R′ = H ( 2a ), CH₃ ( 2b ), CH₂CH(CH₃)₂ ( 2c ), CH₂CONH₂ ( 2d ), CH₂CH₂CONH₂ ( 2e ), CH₂CH₂CH₂CH₂ NHOCOC(CH₃)₃ ( 2f )] were synthesized in good yield by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids with hydroxy groups of HPC ( 1 ; molar substitution (MS), 4.61). The amino acid functionalities displaying varied chemical nature, shape, and bulk were utilized and the bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). The ¹H NMR spectra and elemental analysis were employed to determine the degree of incorporation of amino acid moiety (DS_Est) and almost complete substitution of the hydroxy protons was revealed for 2a , 2b , and 2f . The presence of the peaks characteristic of the carbonyl group in the FTIR spectra furnished further evidence for the successful esterification of HPC. The starting as well as the resulting polymers ( 1 and 2a – f ) were soluble in polar organic solvents; however, the esterification of 1 with bulky organic moieties resulted in an increased hydrophobicity as all of the amino acid‐functionalized polymers ( 2a – f ) were insoluble in water. The onset temperatures of weight loss of 2a – f were 175–230 °C, indicating fair thermal stability. The amino acid functionalization led to the enhanced polymer chain stiffness, and the glass transition temperatures of the derivatized polymers were 30–40 °C higher than that of 1 (T_g 3.9 °C; cf. T_g of 2a – f , 35.1–43.3 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2326–2334, 2008     

A general synthetic route to nanofibers of polyaniline derivatives

Nanofibrous mats of a wide variety of polyaniline derivatives can be synthesized without the need for templates or functional dopants by simply introducing an initiator into the reaction mixture of a rapidly mixed reaction between monomer and oxidant.     

A facile synthesis of p- and m-(amidinomethyl)phenyl esters derived from amino acid and tryptic hydrolysis of these synthetic inverse substrates

A facile synthetic method for p- and m-(amidinomethyl)phenyl esters derived from a variety of amino acids is presented. We analyzed the kinetic behavior of trypsin towards these synthetic esters, which are inverse substrates. The substituent (meta- and para-isomers) and isosteric effects of (amidinomethyl)phenyl esters are discussed.     

Cobalt-catalyzed one-pot three-component coupling route to beta-acetamido carbonyl compounds: a general synthetic protocol for gamma-lactams

An efficient improved procedure for the synthesis of beta-acetamido carbonyl compounds is developed by a cobalt(II) chloride-catalyzed three-component coupling protocol. The procedure is also amenable to the synthesis of gamma-lactams by a three-component coupling reaction with use of 2-carbomethoxybenzaldehyde. The beta-acetamido carbonyl compounds derived from 2-carbomethoxybenzaldehyde are useful intermediates as they can be transformed to the corresponding gamma-lactams on treatment with base.     

Simple synthetic route to chrysanthemic acid and hemicaronic aldehyde

3-cyano-2,2-dimethyl cyclopropane-1-carboxylic acid obtained in 62% yield from isobutyraldehyde¹, dimethylmalonate, NBS and NaCN is readily transformed to tittle compounds precursors of potent natural and unatural pyrethrinoic insecticides².     

Selective hydroalkoxycarbonylation of enamides to N-acyl amino acid esters: synthetic applications and theoretical studies

N-acyl amino acid esters are easily accessible from enamides by cobalt-catalyzed hydroalkoxycarbonylation in moderate to excellent yield. An important reaction parameter for selective carbonylation is the use of low hydrogen partial pressure, which prevents hydrogenation as a side reaction. The reported method is applicable to various enamides and alcohols. A DFT calculation of the catalytic cycle explains the preferred pathway of this reaction.     

Synthesis and some physicochemical properties of the carbazine acid silyl esters

Structure of the dimethylcarbazine acid trimethylsilyl ether and pyrolysis of its derivative, the trimethylsilyl ester of N,N-dimethyl-N′-trimethylsilylcarbazine acid, were studied by the metods of X-ray diffraction and gas chromatography/mass spectrometry. The presence of the bifurcated hydrogen bonds between the trimethylsilyl dimethylcarbazinate molecules was detected. It was revealed why impossible to obtain dimethylaminoisocyanate even by the low-temperature pyrolysis.     

Versatile synthetic route to carbocyclic N-Acetylneuraminic acid and its derivatives

Sialic acid (N-acetylneuraminic acid) is a carbohydrate that possess a nine carbon backbone, and it is often found at the termini of glycoconjugates in biological systems. Because of this prominence many syntheses have reported routes to sialic acid and many of its derivatives. Most of these compounds retain the endocyclic oxygen atom that becomes part of the ketal glycosidic linkage that joins sialic acid to the penultimate residue in the glycoconjugate. With respect to carba-sialic acid (replacement of the ring oxygen atom with a methylene group) a single synthesis has been reported (Ogawa et al. (Carbohydr. Res., 1995, 269, 53–78) in 30 steps and 0.5% yield. The current report details a robust synthesis of 6a-carba-α-d-sialic acid that involves 18 steps and give a 5% yield using d-quinic acid as the starting material.     

A new synthetic route to 4,6-diarylpyridazinones and some of their derivatives

A novel approach to the titled ring system starting from conveniently available chalcones 1 is proposed. It involves a catalysed exchange of hydrogen cyanide between acetone cyanohydrin and 1 . The resulting γ-ketonitriles 2 give the expected 4,6-diarylpyridazinones 4 and 5 via hydrolysis and cyclisation by hydrazine. The action of phosphorus oxychloride on 5 followed by that of amines provides aminopyridazines 7 .     

Carbon-13 and proton magnetic resonance studies of some carbonyl-bis-(amino acid esters)

A number of carbonyl-bis-(amino acid esters) have been examined by proton and carbon-13 nuclear magnetic resonance techniques. All but one of the compounds were synthesized with two chiral centers of like-configuration. In one series, the diastereotopic nonequivalence of isopropyl methyl groups attached to the asymmetric centers is apparent in both the proton and the carbon spectra, and the relative magnitude of the observed nonequivalence increases slightly with increasing ‘bulk’ of the neighboring ester groups. Carbon-13 chemical shifts are reported, and a linear correlation of Taft σ* inductive constants with ester carbonyl carbon chemical shifts and with amide proton chemical shifts (for a series in which only variation of the ester substituent occurs) is presented. In addition, the effect in terms of chemical shift differences of keeping the same ester group at the asymmetric centers while varying the other substituent group, is examined.