Effect of catalytic alkali metal bromide on Hofmann-type rearrangement of imides

The Hofmann-type rearrangement of aromatic and aliphatic imides using KBr as the catalyst proceeded to provide aromatic and aliphatic amino acid derivatives. We have also developed a new synthetic route to gabapentin with this method.     

A four-component, one-pot synthesis of highly substituted 1,4-dihydro-1,8-naphthyridine-3-carboxamides

A new, one-pot, four-component reaction for the synthesis of a novel class of highly substituted 1,4-dihydro-1,8-naphthyridine-3-carboxamide derivatives starting from readily available inputs including aliphatic or aromatic amines, diketene, aromatic aldehydes, and 2-aminopyridines in the presence of a catalytic amount of p-toluenesulfonic acid under mild reaction conditions and in good yields at ambient temperature is described.     

Catalyst-free water-mediated N-Boc deprotection

A catalyst-free water-mediated N-Boc deprotection of N-Boc-amines is reported. In the absence of any additional reagents, the free amines were formed from a variety of aromatic and aliphatic N-Boc-amines as well as from some N-Boc-amino acid derivatives.     

3-acyl-1,2,3,4-tetrahydropyridine-2,4-diones: Synthesis and chemical properties

N-Substituted 6-methyl-1,2,3,4-tetrahydropyridine-2,4-diones reacted with aliphatic carboxylic acid chlorides in the presence of pyridine or triethylamine to give the corresponding 4-O-acyl derivatives which underwent O,C-migration of the acyl group by the action of 2 equiv of triethylamine and a catalytic amount of 2-hydroxy-2-methylpropanenitrile. Reactions of 3-acyl-6-methyl-1,2,3,4-tetrahydropyridine-2,4-diones thus formed with aliphatic and aromatic amines gave the corresponding enamino derivatives at the side acyl group. Enamino derivatives at the C⁴ =O group were obtained by transformation of 3-acyl-1,2,3,4-tetrahydropyridine-2,4-diones into 3-acyl-4-methoxy-6-methyl-1,2-dihydropyridin-2-ones via alkylation with dimethyl sulfate and subsequent treatment with amines.     

Parikh–Doering oxidation–dehydration–Ugi cyclization cascade in the development of lactams from formidoalkanols (3>chain length>7)

De novo incorporation of N-formylated aminols as strategic substrates in legendary Ugi cyclization. Lactamization of N-formido alkanols is accomplished by a novel Parikh–Doering oxidation–dehydration–Ugi cyclization cascade leading to the formation of lactams up to eight carbons (ring size; n=1–4) in moderate yields using formidoaminol, substituted aniline, and aliphatic/aromatic carboxylic acid derivatives as starting materials.     

Asymmetric carbonyl-ene reaction catalyzed by chiral N,N'-dioxide-nickel(II) complex: remarkably broad substrate scope

Highly enantioselective carbonyl-ene reaction of glyoxal derivatives and glyoxylate with various alkenes was accomplished using a novel nickel(II)-N,N'-dioxide complex under mild conditions, which facilitated the asymmetric synthesis of biologically interesting alpha-hydroxy carbonyl compounds. Various aromatic, aliphatic, and heteroaromatic glyoxal derivatives, as well as glyoxylate, could be tolerated in this system and afforded the corresponding adducts in excellent enantioselectivities (97->99% ee) with high yields. Moreover, the catalyst loading could even be decreased to 1 mol%, while the enantioselectivity was basically maintained.     

Design,Synthesis, EPR‐Studies and Conformational Bias of Novel Spin‐Labeled DCC‐Analogues for the Highly Regioselective Labeling of Aliphatic and Aromatic Carboxylic Acids

Novel types of spin‐labeled N,N′‐dicyclohexylcarbodiimides (DCC) are reported that bear a 2,2,6,6‐tetramethylpiperidinyloxyl (TEMPO) residue on one side and different aromatic and aliphatic cyclohexyl analogues on the other side of the diimide core. These readily available novel reagents add efficiently to aliphatic and aromatic carboxylic acids, forming two possible spin‐labeled amide derivatives with different radical distances of the resulting amide. The addition of aromatic DCC analogues proceeds with excellent selectivity, giving amides where the carboxylic acid is exclusively connected to the aromatic residue, while little or no selectivity was observed for the aliphatic congeners. The usefulness of these adducts in structural studies was demonstrated by EPR (electron paramagnetic resonance) measurements of biradical adducts of biphenyl‐4,4′‐dicarboxylic acids. These analyses also reveal high degrees of conformational bias for aromatic DCC derivatives, which further underlines the powerfulness of these novel reagents. This observation was further corroborated by quantum chemical calculations, giving a detailed understanding of the structural dynamics, while detailed information on the solid state structure of all novel reagents was obtained by X‐ray structure analyses.     

Degradation of aliphatic and aliphatic–aromatic co-polyesters by depolymerases from Roseateles depolymerans strain TB-87 and analysis of degradation products by LC-MS

The degradation activities of bacterium, Roseateles depolymerans TB-87 and its depolymerases Est-H and Est-L against aliphatic as well as aliphatic–aromatic co-polyesters, were investigated. Strain TB-87 and its enzymes exhibited an ability to degrade aliphatic and aliphatic–aromatic co-polyesters. Monomers produced as a result of degradation of aliphatic polyesters [poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBSA)] as well as aliphatic–aromatic co-polyester [poly(butylene succinate/terephthalate/isophthalate)-co-(lactate) (PBSTIL) by depolymerases Est-H and Est-L were investigated by liquid chromatography mass-spectrometry (LC-MS). Some common monomers like succinic acid and 1,4-butanediol were detected besides adipic acid and terephthalic/isophthalic acids as degradation products from PBSA and PBSTIL, respectively, whereas lactic acid was not detected. The succinic acid monomer was detected prior to adipic acid as a result of degradation of PBSA. The enzymes depolymerized PBS also into respective monomers. The analysis of PBSTIL degradation products revealed that enzymes easily degraded aliphatic segments as compared to aromatic segments and resulted in production of succinic acid prior to terephthalic and isophthalic acid. On the basis of these results, we speculate that both the enzymes Est-H and Est-L, attacked succinic acid segments (BS) first instead of adipic acid (BA) and terephthalic/isophthalic acid (BT or BI) segments of PBSA and PBSTIL, respectively. It is concluded from the results that R. depolymerans strain TB-87 can depolymerize aliphatic as well as aliphatic–aromatic co-polyesters; therefore, its enzymes can be applied in the process of biochemical monomer recycling.     

Enantioselective,copper(I)-catalyzed three-component reaction for the synthesis of β,γ-alkynyl α-amino acid derivatives

The first catalytic asymmetric three-component reaction of ethyl glyoxylate, para-anisidine, and aliphatic, aromatic alkynes catalyzed by CuOTf·0.5C₆H₆/pybox 7 has been developed. The protocol provided the corresponding chiral β,γ-alkynyl α-amino acid derivatives in good yields and 66–74% ee.     

Diketene as an alternative substrate for a new Biginelli-like multicomponent reaction: one-pot synthesis of 5-carboxamide substituted 3,4-dihydropyrimidine-2(1H)ones

5-Carboxamide substituted 3,4-dihydropyrimidine-2(1H)one derivatives were synthesized in a simple and efficient method from the one-pot four-component reactions of an aliphatic or aromatic amine, diketene, an aromatic aldehyde and urea or thiourea in the presence of p-toluenesulfonic acid as a catalyst under mild reaction conditions at ambient temperature.     

N-Benzyloxycarbonylation of amines in the ionic liquid [TPA][l-Pro] as an efficient reaction medium

An efficient method for the N-benzyloxycarbonylation of amines is described. The reaction of amines with Cbz-Cl in the ionic liquid [TPA][l-Pro] afforded the corresponding N-Cbz derivatives in excellent yields. The method is versatile for the preparation of a wide variety of N-Cbz derivatives of aliphatic and aromatic amines.     

Asymmetric Organocatalytic Homologation: Access to Diverse Chiral Trifluoromethyl Organoboron Species

A broad range of aliphatic, aromatic, and heterocyclic boronic acids were successfully homologated using trifluorodiazoethane in the presence of BINOL derivatives to provide the corresponding chiral trifluoromethyl containing boronic acid derivatives in high yields and excellent enantioselectivity. The in situ conversion of the chiral transient boronic acids to the corresponding alcohols or β-CF3 carboxylates are also demonstrated.     

Catalytic asymmetric Pictet-Spengler reaction

A catalytic asymmetric Pictet-Spengler reaction has been developed, wherein treating substituted tryptamines with an aldehyde in the presence of a catalytic amount of a chiral phosphoric acid provides the corresponding tetrahydro-beta-carboline derivatives in high yields and enantiomeric excesses. The reaction works well with both aliphatic and aromatic aldehydes.     

Synthesis of fully substituted pyrazolo[3,4-b]pyridine-5-carboxamide derivatives via a one-pot four-component reaction

A one-pot four-component reaction of an aliphatic or aromatic amine, diketene, an aromatic aldehyde and 1,3-diphenyl-1H-pyrazol-5-amine in the presence of p-toluenesulfonic acid as a catalyst has been developed. In this reaction, a new class of fully substituted pyrazolo[3,4-b]pyridine-5-carboxamide derivatives is produced under mild reaction conditions and in good yields at ambient temperature.     

Reduction of phosphine oxides to phosphines with the InBr3/TMDS system

An efficient method for the reduction of phosphine oxide derivatives into their corresponding phosphines is described. The system InBr₃/TMDS allows the reduction of different secondary and tertiary phosphine oxides as well as aliphatic and aromatic phosphine oxides.     

A convenient and efficient method for the synthesis of new 2-(4-amino substituted benzilidine) indanone derivatives

An efficient and improved process for the synthesis of novel 1-indanones derivatives has been developed. In the first step of the presented new process, 4-bromobenzaldehyde reacts with 5, 6-dimethoxy-2, 3-dihydro-1H-inden-1-one by N-arylation of corresponding compounds with a variety of aliphatic and aromatic amines to produce a novel category of 1-indanones as the final step. Comparison of this newly designed method with conventional methods show that our method is much more efficient in producing a higher total yield. This innovative synthesis methodology offers several advantages, among which the consumption of inexpensive reagents and the resulting higher total yields of final products are of its remarkable points.     

Synthesis of zwitterionic compounds: fully saturated pyrimidinylium and 1,3-diazepinylium derivatives via the novel rearrangement of 3-oxobutanoic acid thioanilide derivatives

An unusual rearrangement following cyclization of 2-anilino-2-ethoxy-3-oxothiobutanoic acid with aliphatic 1,3- as well as 1,4-diamine leads to zwitterionic derivatives of 2-hydroxypropanoic acid. Moreover, with aromatic 1,2-diamines, fused heterocyclic systems such as pteridine, quinoxaline, and pyrido[2,3-b]pyrazine are obtained.     

A combinatorially convenient version of synthesis of 5-substituted oxazole-4-carboxylic acid ethyl esters

Reaction of ethyl isocyanoacetic acid with sodium hydride in anhydrous benzene, followed by treatment with carboxylic acid chlorides or N-(acyloxy)pyrrolidine-2,5-diones, gives 5-substituted oxazole-4-carboxylic acid esters. The procedure is applicable to derivatives of various carboxylic acids, including saturated aliphatic, α,β-unsaturated, alicyclic, aromatic, heterocyclic, and N-Boc-protected amino acids.     

Effective esterification of carboxylic acids using (6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl ester as novel coupling agents

(6-Oxo-6H-pyridazin-1-yl)phosphoric acid diethyl esters (3) are efficient and selective coupling agents for equimolar esterification of carboxylic acids and alcohols. Esterification of aliphatic and aromatic carboxylic acids with aliphatic and aromatic alcohols using 3 afforded the corresponding esters chemoselectively in good to excellent yield.     

Analysis of Non-volatile Constituents in Dracocephalum Species by HPLC and GC-MS

In this paper we identify/determine the composition of the extracts of Dracocephalum moldavica L. and D. ruyschiana L. with special emphasis on their flavonoids, aliphatic, aromatic carboxylic acids and sugars. The plant materials were extracted using methanol-acetone 1:1 (v/v) acidified with HCl (0.05%). Composition of extract's most red fractions was identified by HPLC, while the constituents of the entire extract were identified and quantified as their trimethylsilyl-(oxime) ether/ester derivatives by GC-MS. On the basis of HPLC analyses - (performed on Phenomenex Luna 5 µm C18 column, 250× 4.6 mm I.D.; eluent: acetonitrile - trifluoroacetic acid (0.1 %); isocratic/gradient conditions) - delphinidin, cyanidin and pelargonidin (in traces) were identified by spectral analysis and on the basis of authentic standard's addition. GC-MS analyses were carried out immediately with extracts, as well as subsequently to extract's hydrolysis (trifluoroacetic acid: 2M, 2h, 4h). Constituents were identified and quantified as their trimethylsilyl-(oxime) ether/ester derivatives, from a single run, on the basis of their total (TIC) and selective fragment ion (SIM) responses. Calculations were related to the dry matter content of extracts. As main constituents monosaccharides, sugar alcohols di- and trisaccharides, aliphatic (phosphoric, succinic, levulinic, malic, tartaric, fatty acids) and aromatic (quinic, chlorogenic, caffeic, ferulic, 3,4-dihydroxyphenyllactic, rosmarinic) carboxylic acids and their corresponding esters; apigenin, luteolin flavon aglycons and tocopherol, in total 33 constituents were quantitated partly by their TIC, partly by their SIM responses. Identification/quantification proved to be in total of 35–69% (expressed in the dry matter content of extracts).