Trifluoromethanesulfonylimides of arenehydroxamic acids and their aza Lossen rearrangement

Trifluoromethanesulfonylimides of arenehydroxamic acids ArC(NSO₂CF₃)NHOH (1), analogues of arenehydroxamic acids, in which sp² hybridized oxygen atom is replaced by the much stronger electron-withdrawing group NSO₂CF₃, have been synthesized, and the abilities of these compounds to undergo transformations similar to the Lossen rearrangement have been studied.At heating O-trimethylsilyl or O-tosyl derivatives of acids 1 rearrange to carbodiimides ArNCNSO₂CF₃ or products of their hydration, the corresponding carbamides. Interaction of acids 1 with sulfinyl chloride or phosphorus pentachloride results in formation of N-trifluoromethylsulfonyl-N′-arenechloroformamidines, ArNHC(Cl)NSO₂CF₃, which were transformed into their morpholine derivatives and thus characterized.     

Amidine derivatives of α-arylglycines from N-(1-aryl-2,2,2-trichloroethyl)amides of arenesulfonic acids and secondary amines

The interaction of N-(1-aryl-2,2,2-trichloroethyl)amides of arenesulfonic acids with secondary amines or their salts in the presence of inorganic bases involves the formation of chloroaziridine intermediates. Depending upon the solvent and reagent ratio, the reaction results in N-[1-dialkylamino-2-chloro-2-arylethylidene]-, N-[2-dialkylamino-1-chloro-2-arylethylidene]-, N-[1,2-bis(dialkylamino)-2-arylethylidene]-, and N-(1,2-dioxo-2-arylethene)amides of arenesulfonic acids.     

N-phosphanylamidine ligands and their catalytic activity in the hydroformylation of 1-octene and styrene

Pyridine-based N-phosphanylamidine ligands i-Pr₂N-C(pyr)N-PR₂ (R = Ph (3), i-Pr (4)) were synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Mononuclear rhodium complexes 7 and 8 were obtained in one step from the [RhCl(COD)]₂ dimer and the monodentate ligands 1 and 2. Their single-crystal X-ray diffraction studies revealed the structural adaptive behavior of the monodentate N-phosphanylamidine ligands 1 and 2 upon k¹-P coordination mode in rhodium(I) complexes with the imino nitrogen atom of the amidine function which behaves as a “universal joint”. Compounds 1-4 were evaluated as ligands in the 1-octene and styrene hydroformylation reactions. The results obtained are encouraging and represent the first report on the use of N-phosphanylamidine ligands of the type R″₂N-C(R′)N-PR₂ in catalytic reactions.     

Synthesis of 5-trichloromethyl-Δ-1,2,4-oxadiazolines and their rearrangement into formamidine derivatives

A series of 5-trichloro-Δ⁴-1,2,4-oxadiazolines have been synthesised by 1,3-dipolar cycloaddition of nitrones to trichloroacetonitrile. These oxadiazolines rearrange into formamidine derivatives, via ring opening and a 1,2-aryl shift from carbon to the adjacent amino nitrogen. Both cycloaddition and rearrangement are facilitated when electron deficient nitriles and electron rich nitrones are used.     

Photo-Fries rearrangement of N-arylsulfonamides to aminoaryl sulfone derivatives

Photochemical reaction of variously substituted p-toluenesulfonanilides was studied. The reaction gives rearranged products, o- and p-amino-substituted diaryl sulfones with the combined yields of 38-72%: the p-isomer is more favored over the o-isomer with the selectivity ratio of 1.1-4.3 depending on the substituents. N-Alkylation of the sulfonanilides increases the yields of the rearranged products, and e-withdrawing substituents on the N-phenyl ring does not lower the yields drastically. This study provides simple methodology for the synthesis of o- and p-aminoaryl sulfones which are otherwise not easily accessible.     

A new route to (±)-erythro-roccellic acid and chaetomellic anhydride C through functional rearrangement, promoted by n-propylamine or CH3ONa/CH3OH, of N-propyl-3-chloro-4-dichloromethyl-3-dodecylpyrrolidin-2-one

The rearrangement of a trichloro-pyrrolidin-2-one, prepared by the CuCl-TMEDA catalyzed atom transfer radical cyclization of N-alkyl-N-(3-chloro-2-propenyl)-2,2-dichloromyristamide, with n-propylamine or CH₃ONa/CH₃OH, is the key step of a new, short and inexpensive route to chaetomellic anhydride C and (±)-erythro-roccellic acid.     

Microwave-assisted synthesis of N-glycolylneuraminic acid derivatives

A rapid, efficient and scalable synthesis of biologically-relevant N-glycolylneuraminic acid derivatives from the natural N-acetyl (Neu5Ac) precursors has been developed. Microwave irradiation provides accelerated de-N-acetylation compared to more traditional methods, with optimised NaOH-promoted de-N-acetylation in only 15 min. The prepared amines were readily re-N-acylated to afford the corresponding N-glycolyl (Neu5Gc) analogues.     

Base-promoted aromatic [3,3] sigmatropic rearrangement of N-acyl-O-arylhydroxylamine derivatives

The base-promoted aromatic [3,3] sigmatropic rearrangement of N-acyl-O-arylhydroxylamines giving α-(2-hydroxyphenyl)amides was successfully demonstrated. The substrates were prepared from N-substituted hydroxylamines by N-acylation followed by copper(I)-mediated O-arylation with boronic acids. Treatment of the substrates with lithium hexamethyldisilazide (LiHMDS) in THF at 0?°C to room temperature generated the corresponding amide enolates. The aromatic [3,3] rearrangement of the enolates provided the desired products in moderate to good yields. A crossover experiment produced only intramolecular products and clarified that the reaction proceeds via the aromatic [3,3] sigmatropic rearrangement, not a bond-cleavage–recombination process. Our method is a formal α-arylation of amides.     

Lewis acid promoted aza Diels-Alder reactions of acyclic unactivated 5-dienyl pyrimidinones with N-arylimines: synthesis of novel quinoline derivatives

The chemo- as well as regioselective aza Diels-Alder reactions of 5-dienyl pyrimidinones with N-arylimines in the presence of a Lewis acid catalyst resulting in novel quinoline derivatives are reported.     

Synthesis of functionalised azecine and azonine derivatives via an enolate assisted aza Claisen rearrangement

This paper describes the synthesis of functionalised azecine and azonine derivatives incorporating the adrenaline motif. In a key step, an enolate assisted aza Claisen rearrangement was employed to interconvert from 6- and 5-membered heterocycles to their corresponding 10- and 9-membered lactams.     

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, structural characterisation and biological activity of novel N-(ferrocenylmethyl)benzene-carboxamide derivatives

A series of N-(ferrocenylmethyl)benzene-carboxamide derivatives (4a-f) have been synthesised by coupling ferrocenylmethyl amine 3 with benzoic acid and various substituted fluorobenzoic acids using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. All compounds were fully characterised using a combination of ¹H NMR, ¹³C NMR, ¹⁹F NMR, DEPT-135, ¹H-¹H COSY and ¹H-¹³C COSY (HMQC) spectroscopy and electrospray ionisation mass spectrometry (ESI-MS). The compounds 4a, 4d, 4e and 4f exhibited cytotoxic effects on the MDA-MB-435-S-F breast cancer cell line. Single crystal X-ray crystallographic data for 4d is also presented.     

Synthesis of the end-capped 5-(N,N-dimethylamino)naphthyl-1-ethynyl derivatives and their 1,4-di[5-(N,N-dimethylamino)naphthyl]-1,3-butadiynes: anti rotamer structure

A new family of the end-capped 5-(N,N-dimethylamino)naphthylethynyl chains were synthesized, as terminal acetylenes or poly(yne) structures, by heterocoupling between 5-iodo-N,N-dimethylnaphthalen-1-amine and 2-methyl-3-butyn-2-ol or 4-(5-iodo-1-naphthyl)-2-methyl-3-butyn-2-ol, catalyzed by the palladium-copper system. Catalytic homocoupling of the terminal acetylenes, affords to 1,4-dinaphthyl-1,3-butadiyne nanostructures. X-ray diffraction analysis of 1,4-di(α-naphthyl)-1,3-butadiyne shows that the naphthalene rings are in the anti configuration along the acetylene axis. All the conjugated compounds show an important fluorescent emission radiation.     

Studies on the Lossen-type rearrangement of N-(3-phenylpropionyloxy) phthalimide and N-tosyloxy derivatives with several nucleophiles

The reaction of N-(3-phenylpropionyloxy)phthalimide (1a) and N-tosyloxy (5a,b) derivatives with nucleophiles was examined and found to give the products via Lossen-type rearrangement. In order to obtain the scope of this reaction mechanism, further studies the reaction of several N-sulfonyloxyimide derivatives with various nucleophiles under similar conditions were carried out and found to afford the corresponding same types of products in high yields.     

Electrochemical oxidation of N-methylated derivatives of uric acid

The electrochemical oxidation of a number of N-methylated uric acids has been studied by linear and cyclic sweep voltammetry, coulometry and thin-layer spectroelectrochemistry. The observed results support the view that the electrooxidation is a 2e reaction to give a very unstable diimine primary product. This is rapidly hydrated to give an imine-alcohol which is further hydrated to give a uric acid-4,5-diol derivative which subsequently fragments to the various products.     

Synthesis of p-amino-N,N′-dihydroxybenzamidine using a TBDMS protecting group protocol

A synthetic route to p-amino-N,N′-dihydroxybenzamidine is established using a TBDMS protecting group strategy starting with p-nitrobenzhydroxamic acid chloride, which is transformed to O,O′-bis(tert-butyldimethylsilyl)-N,N′-dihydroxybenzamidine. Reduction with sodium dithionite occurs without degradation of the dihydroxyamidine functional group. Deprotection with ammonium fluoride is fast and efficient. This is important because no other possibility to synthesize this derivative has been found up to now. Furthermore, TBDMS protecting group strategy is proved to be adaptable to other substituted N,N′-dihydroxybenzamidines.     

Structural homologies in benzylamino-N,N-bis methylphosphonic acid and its layered zirconium derivative

A new layered zirconium diphosphonate fluoride, ZrF(O₃PCH₂)₂NHCH₂C₆H₅ has been prepared and its structure determined ab initio by X-ray powder data and refined with the Rietveld method (orthorhombic, , , , space group Pbca, , Z=8, R_wp=0.080). Both phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of each layer. Benzyl groups from adjacent layers are interdigitated in the interlayer region, with probable π-π stacking interactions. The structure of the free benzylamino-N,N-bis methylphosphonic acid has been determined by single crystal X-ray data (monoclinic, space group P2₁, , , , β=92.930(3)°, , Z=2, R₁=0.072, wR₂=0.150). As in the zirconium derivative, benzyl groups from adjacent layers are interdigitated and create a regular alternation of polar and non-polar regions.     

Quantum-chemical study of aza derivatives of styrylnaphthalenes and their photocyclization products

Quantum-chemical calculation of 1- and 2-styrylnaphthalenes and their aza derivatives 2- and 4-styrylquinolines were carried out by the DFT B3LYP/6-31G* method. The relative stability of the products of their photoisomerization, (E)- and (Z)-isomers and of the photocyclization products, the corresponding derivatives of dihydrophenanthrene (DHP), was calculated. It has been shown that, by the DHP stability, the diarylethylenes in question are divided into two groups in qualitative agreement with experimental data on their photochemical activity in the photocyclization reaction.