The reaction of β-lactam carbenes with 3,6-di(2-pyrimidinyl)tetrazine: regulating products by reaction conditions

The reaction of β-lactam carbenes with 3,6-di(2-pyrimidinyl)tetrazine was studied, which produced good yields of novel 5-(3-[1,2,3]triazolo[1,5-a]pyrimidinyl)pyrrol-2-ones or pyrrolo[3′,2′:3,4]pyrrolo[1,2-a]pyrimidin-2-ones under heating at 100 °C or 140 °C, respectively. This work provided a highly efficient strategy for the construction of both [1,2,3]triazolo[1,5-a]pyrimidine and pyrrolo[3′,2′:3,4]pyrrolo[1,2-a]pyrimidine ring systems from the same reactants, and extended the application of β-lactam carbenes in the syntheses of complex heterocycles.     

Interaction of β-lactam carbenes with 3,6-diphenyltetrazines: a five-step cascade reaction for the direct construction of indeno[2,1-b]pyrrol-2-ones

A study of the nucleophilic addition of β-lactam carbenes to 3,6-diphenyltetrazines is reported. Instead of the formation of pyrazole derivatives like most reactions between nucleophilic or ambiphilic carbenes and 3,6-disubstituted tetrazines, β-lactam carbenes reacted with 3,6-diphenyltetrazines to produce indeno[2,1-b]pyrrol-2-ones in good yields. The reaction proceeds most probably through a five-step cascade process. This work has not only provided a one-pot operation for the efficient construction of mutisubstituted indeno[2,1-b]pyrrol-2-ones but also revealed the nucleophilicity of β-lactam carbenes.     

The reaction of carbohydrates and uronic acids with β-methylindole

Aldo- and ketu-hexoses produce with β-methylindole a pigment that is soluble with blue color in chloroform. The same applies to ω-hydroxymethylfurfural. Pentoses and uronic acids as well as furfural produce an olive color reaction, but no blue Soluble pigment. Methylpentoses and methylfurfural produce a red pigment, the chloroform extract of which is of raspberry color. The behavior of the heptoses is not characteristic. There is no possibility of differentiating between glucurone and galacturonic acid.     

Concurrent cyclopropanation by carbenes and carbanions? A density functional theory study on the reaction pathways

The mechanisms for the addition reactions of phenylhalocarbenes and phenyldihalomethide carbanions with acrylonitrile (ACN) and trimethylethylene (TME) have been investigated using an ab initio BH and HLYP/6-31G (d, p) level of theory. Solvent effects on these reactions have been explored by calculations that included a polarizable continuum model (PCM) for the solvent (THF). These model calculations show that for the addition of phenylhalocarbenes, a TME species may readily undergo addition reactions with carbenes while ACN has a high-energy barrier to overcome. It was also found that phenyldihalomethide carbanions do not readily add to the electron-rich TME. The cyclopropane yields only appear to occur via addition of PhCBr to TME. However, the cyclopropanation proceeds not only via slow addition of phenylhalocarbenes to ACN but also forms through the stepwise reaction of phenyldihalomethide carbanions with ACN. Our calculation results are in good agreement with experimental observations (Moss, R.A.; Tian, J.-Z. J. Am. Chem. Soc. 2005, 127, 8960) that indicate that the cyclopropanation of phenylhalocarbenes and phenyldihalomethide carbanions with ACN are concurrent in THF.     

The role of β-bulky substituents in aldol reactions of boron enolates of methylketones with aldehydes: experimental and theoretical studies by DFT analysis

In this work, we show the influence of the volume of the β-substituents on the levels of 1,5-stereoselectivities of aldol reactions of boron enolates generated from β-alkoxy methylketones with aldehydes. Excellent levels of 1,5-syn stereoinduction were obtained when the β-protecting group is a silicon ether. This remarkable selectivity is attributed to the volume of the β-bulky substituent of the corresponding boron enolate. We have investigated a stereochemical model using DFT analysis to rationalize the sense of 1,5-syn stereoselectivities of β-alkyl-β-alkoxy methylketones.     

Reaction of β-lactam carbenes with 2-pyridyl isonitriles: a one-pot synthesis of 2-carbonyl-3-(pyridylamino)imidazo[1,2-a]pyridines useful as fluorescent probes for mercury ion

The one-pot reaction of β-lactam carbenes with 2-pyridyl isonitriles followed by an acidic hydrolysis was reported, which produced 2-carbonyl-3-(pyridylamino)imidazo[1,2-a]pyridines in moderate to good yields. Among the resulting novel imidazo[1,2-a]pyridine derivatives, 1-(6-chloro-3-(5-chloropyridin-2-ylamino)imidazo[1,2-a]pyridin-2-yl)-2-ethylbutan-1-one was demonstrated to be an efficient fluorescent probe for mercury ion both in acetonitrile and in buffered aqueous solution.     

Synthesis of 4-aryl-substituted β-lactam enantiomers by enzyme-catalyzed kinetic resolution

Enantiopure 4-phenyl- and 4-(p-tolyl)-2-azetidinones 3a, 3b, 4a and 4b (with e.e.s of ≥96%) were prepared through lipase-catalyzed asymmetric butyrylation of the primary OH group of N-hydroxymethylated β-lactams (±)-5 and (±)-6 at the (R)-stereogenic centre or by lipase-catalyzed asymmetric debutyrylation of O-butyryloxymethyl-2-azetidinones (±)-7 and (±)-8 at the (R)-stereogenic centre. The ring-opening of lactams 5a, 5b, 6b and 8a with HCl/EtOH afforded the corresponding β-amino ester enantiomers 9a, 9b, 10a and 10b with e.e.s of ≥92%.     

The reaction of carbohydrate-derived alkoxyaldehydes with methoxycarbonylmethylenetriphenylphosphorane: stereoselective synthesis of β-unsaturated esters

The reaction of several carbohydrate-derive alkoxyaldehydes with methoxycarbonylmethylenetriphenylphosphorane afford α, β-unsaturated esters with Z-stereoselectivity. The stereoselectivity depends on the substrate stucture and the nature of the solvent used.     

The reaction of β-dicarbonyl compounds with trifluoromethyl-sulphenyl chloride Part II. The synthesis of 3-SCF3 substituted 2- and 4-quinolinones

3-SCF₃ substituted 4-methyl-2(1H)-, 4-phenyl-2(1H)-, 2-methyl-4(1H), and 2-phenyl-4(1H)-quinolinones were obtained by cyclization of the respective -SCF₃ submitted acetoacetanilides or benzoylacetanilides or their β-phenylimino analogues in concentrated sulphuric acid upon heating. The structures of the compounds obtained were elucidated by elemental analysis and their IR, ¹H and ¹⁹F NMR, and mass spectra.     

Characterization of isomeric cationic porphyrins with β-pyrrolic substituents by electrospray mass spectrometry: The singular behavior of a potential virus photoinactivator

Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) have been used to differentiate the 2- and 4-methylpyridyl isomers of free-base and metallated cationic beta-vinylpyridylporphyrins. The analysis by ESI-MS/MS of the deuterated analogs and semiempirical calculations of structural and electronic parameters were also undertaken. The two free-base isomers are easily differentiated by ESI-MS/MS but the presence of a metallic center renders differentiation of the metallated isomers less effective. The data acquired show that of all the studied compounds, the free-base 2-methylpyridyl isomer, which was operative in the in vitro photoinactivation of Herpes simples virus, has a different gas-phase behavior. Local distortion of the macrocycle due to the presence of the beta-vinylpyridyl substituent occurs for all the compounds, but a different electron density distribution can account for the observed gas-phase behavior of this potential virus photoinactivator.     

Formation of acridones by ethylene extrusion in the reaction of arynes with β-lactams and dihydroquinolinones

N-Unsubstituted β-lactams react with a molecule of aryne by insertion into the amide bond to form a 2,3-dihydroquinolin-4-one, which subsequently reacts with another molecule of aryne to form an acridone by extrusion of a molecule of ethylene. 2,3-Dihydroquinolin-4-ones react under the same reaction conditions to afford identical results. This is the first example of ethylene extrusion in aryne chemistry.     

The acetonation of lactose and benzyl β-lactoside with 2-methoxypropene

The acetonation of lactose with 2-methoxypropene afforded 4,6-O-isopropylidene lactose (2) and a diacetal which, after acetylation, gave an α,β-anomeric mixture of 1, 2,6,3'-tetra-O-acetyl-3,2':4',6'-di-O-isopropylidene lactose (4). Acetonation of benzyl b-lactoside afforded the mixed acetals benzyl 6,6'-di-O-(methoxydimethyt)methyl (6), 6'-O-(methoxydimethyl)methyl-(7) and 6-O-(methoxydimethyl) methyl-β -lactoside (8), the cyclic acetal benzyl 4',6'-O-isopropylidene.-β-lactoside (9) and a diacetal which, after acetylation gave benzyl 2, 6, 3'-tri-O-acetyl-3,2':4',6'-di-O-isopropylidene-β-lactoside (11). The favoured formation of eight-membered 3,2'-cyclic acetals in lactose derivatives has been further demonstrated by acetonation of benzyl 2,3',6'-tri-O-benzyl-β-lactoside (13) and benzyl 2,6,3',6'-tetra-O-benzyl-b-lactoside (12). As an example of the synthetic utility of this acetonation reaction, the chiral macrocyclic polyhydroxyether 25 has been synthesized from benzyl 3',4'-O-isopropylidene-β-lactoside.     

Synthesis of highly functionalized β-lactam substituted pyrroloisoquinoline and indolizinoindole system by sequential intermolecular 1,3-dipolar cycloaddition reaction and Pictet-Spengler cyclization

Synthesis of novel pyrroloisoquinoline and indolizinoindole derivatives with β-lactam unit has been achieved by sequential intermolecular 1,3-dipolar cycloaddition reaction and Pictet-Spengler cyclization. The azomethine ylide derived from β-lactam imine of α-amino ester in the presence of silver acetate reacted with nitrostyrenes to give pyrrolidinyl β-lactam, which underwent Pictet-Spengler cyclization in presence of trifluoroacetic acid to give pyrroloisoquinolines and indolizinoindoles.     

Convenient syntheses of cyclic carbonates by new reaction of oxiranes with β-butyrolactone

Cyclic carbonates were synthesized by reactions of the corresponding oxiranes with β-butyrolactone using quaternary salts such as tetrabutylammonium bromide or 18-crown-6 = KBr as a catalyst.     

Photoelectron spectra and electronic structure of boron difluoride β-diketonates with aromatic substituents

The electronic structure of boron difluoride chelate complexes of the acetyl acetonate type containing 4-biphenylene, 2-fluorene and 4-trans-stilbene as β-substituents is studied by means of photoelectron spectroscopy and quantum chemistry in the DFT approximation. It is established that the substituents affect the nature and sequence of the spectral bands. It is shown that calculation results corrected to the value of the Koopmans defect reproduce quite well the energy intervals between ionized states of complexes.     

The reaction of trifluoromethanesulfenyl chloride with enamines of β-keto carboxylic acid anilides

1-Morpholino-cyclopenten-2-carboxylic acid anilides react with CF₃SCl in molar ratio 1:2 to give products of the displacement of two hydrogen atoms at C-2 and C-5. The analogous reaction with enamines of cyclohexanono- and cycloheptanono- 2-carboxylic acid anilides and benzoylacetanilides proceeds in 1:1 molar ratios affording enamines and keto compounds.     

Revisiting the reaction of β-chloroacroleins with 2-aminophenol: a new observation

The reaction of β-chloroacrolein with 1 equiv of 2-aminophenol in DMF proceeds smoothly to afford 11-hydroxy derivative of chromenoquinoline in good yield. This single pot method allows for a rapid access to a variety of chromenoquinolines or oxepinoquinolines depending on the nature of β-chloroacrolein used. The structures were established by spectroscopic data and further confirmed by X-ray diffraction analysis. A plausible mechanism for this reaction has been proposed. The reaction seemed to proceed via a chloroimine species, whose intermediacy has been established, followed by the construction of the fused quinoline ring.     

The thermal stabilities of luminescence and microstructures of Eu2+-doped KBaPO4 and NaSrPO4 with β-K2SO4 type structure

Eu(2+)-doped monophosphates NaSrPO(4) and KBaPO(4) with the β-K(2)SO(4) structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu(2+) emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO(4):Eu(2+) and KBaPO(4):Eu(2+) were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO(4):Eu(2+) presents only one emission center; however, Eu(2+) ions have a "disordered environment" in NaSrPO(4) lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu(3+) ions in the (7)F(0)→(5)D(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO(4), the Eu(3+) ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu(3+) ions with highly disordered distributions in NaSrPO(4) lattices was suggested.