Synthesis of 1,2-dihydroxyindolizidines from 1-(2-pyridyl)-2-propen-1-ol

1-(2-Pyridyl)-2-propen-1-ol, obtained by vinylation of commercially available picolinaldehyde, resulted a good starting material for the synthesis of the indolizidine skeleton. In particular, a simple process involving bromination, reduction, and nucleophilic substitution (via elimination and addition) allowed an easy conversion of the starting material into (±)-lentiginosine in ~27% overall yield.     

Hyperfine resolved spectrum of the bromomethyl radical, CH2Br, by Fourier transform microwave spectroscopy

Pure rotational spectra of the bromomethyl radical, CH(2)Br, were measured by using a Fourier transform microwave (FT-MW) spectrometer in order to fully resolve hyperfine structures arising from both the bromine and hydrogen nuclei. We detected a total of 124 lines for the (79)Br and (81)Br isotopomers, including K(a)=0 (ortho species) and K(a)=1 (para species). No hyperfine splitting due to the hydrogen nuclei was observed for the para species, directly confirming the planarity of the radical. We conducted a global analysis of our present FT-MW results and previous measurements in the millimeter-wave region and obtained an exhaustive list of molecular constants. The sign of the Fermi constant of the bromine nucleus was unambiguously determined to be positive, which is opposite to that found in previous work in the millimeter-wave region and in electron spin resonance experiment on this radical. The present study permitted a systematic comparison to be made of the hyperfine coupling constants of both the halogen and hydrogen nuclei for CH(2)X-type compounds, where X=F, Cl, and Br.     

New reactivity of 1-(2-pyridyl)-2-propen-1-ol with nitro derivatives

1-(2-Pyridyl)-2-propen-1-ol showed an unprecedented reactivity behaving as Hantzsch ester 1,4-dihydropyridine mimic for the metal-free reduction of the nitro group of electron-deficient aromatic and heteroaromatic nitro compounds to the corresponding amino function. The redox mechanism is part of a domino process involving a direct trapping of the amino derivatives through aza-Michael addition to the vinyl ketone intermediate leading to the one-pot formation of new functionalised aminoacylpyridines.     

New Preparation of (Z)-1-Phenyl-3-cyano-2-propen-1-ones

Reaction of γ-phenyl-β,γ-unsaturated hydroxamates with bis(collidine)bromine(I) hexafluorophosphate led to the formation of cyclic bromo imidates. Reaction of these with triethylamine led to the formation of 3-cyano-2-propen-1-ones with good yields by a fragmentation reaction.     

1-(2-Pyridyl)-2-propen-1-ol: a multipurpose reagent in organic synthesis

A peculiar thermal behaviour of hydroxyallylpyridyl derivatives, likely associated to the weak acidity of the ‘picoline-type’ hydrogen atom and responsible for the formation of allyl inversion products, has been reported. The ‘mobility’ of the same hydrogen atom allowed the unprotected title compound to behave regioselectively as C-1, C-2 or C-3 carbon nucleophile depending on the thermal or base-promoted experimental conditions and on the kind of electrophile; moreover, the corresponding Hantzsch-type pyridine tautomer displayed a biomimetic ability to transfer hydrogen to aromatic and heteroaromatic nitro derivatives.     

Hyperfine spectrum of RbCl

The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectrum of the four isotopomers of RbCl. Coupling constants for the nuclear electric quadrupole interactions, the spin-rotation interactions, the tensor and scalar spin-spin interactions, and a rubidium nuclear octupole interaction, and their dependence on vibrational and rotational states have been determined. The dominant interaction, the rubidium nuclear electric quadrupole interaction, shows a small shift with substitution of the chlorine isotope.     

Synthesis of Boron-containing Complexes of 1-(2-hydroxyphenyl)-3-phenyl-2-propen-1-one

Condensation of o-hydroxyacetophenone with benzaldehyde in alcohol in the presence of a triple excess of a sodium hydroxide solution leads to 2'-hydroxychalcone sodium salt. The latter was heated with boron trifluoride etherate in toluene to a 2'-hydroxychalcone boron fluoride complex in which the boron atom is coordinated to the carbonyl oxygen atom. The same complex was obtained by boiling of the o-hydroxyacetophenone boron fluoride complex with benzaldehyde in acetic anhydride.     

The microwave spectrum of dichlorosilylene (SiCl2) in excited vibrational states

The microwave spectrum of dichlorosilylene in excited vibrational states has been measured in the millimetre- and submillimetre-wave regions. Rotational and centrifugal distortion constants were determined for the ν₁, ν₂, 2ν₂ and ν₃ excited states of the Si³⁵Cl₂ isotopic species and for the ν₂ and 2ν₂ states of Si³⁵Cl³⁷Cl. Analysis of the Coriolis resonance between the ν₁ and ν₃ states of Si³⁵Cl₂ yielded values of the D Coriolis interaction constant with F constrained, of two higher-order terms and also an accurate value [5.402338(95) cm⁻¹] of the energy difference between the two excited vibrational states. The rotational constants of Si³⁵Cl₂ in the first excited states of the three normal vibrations were combined with those of the ground vibrational state reported in a previous paper [M. Tanimoto et al., J. Chem. Phys. 91, 2102 (1989)] to obtain the equilibrium structure, harmonic and cubic/third-order anharmonic potential constants.     

Crystal Structures of (Z)-1-Phenyl-1-phenylseleno-2-(p-tolylsulfonyl)ethene and (Z)-1,3-Diphenyl-3-phenyl-seleno-2-(p-tolylsulfonyl)-2-propen- 1-ol

1 INTRODUCTION The vinyl sulfones are versatile intermediates in organic chemistry and have been extensively stu- died[1]. The available methodology for vinyl sulfone synthesis mainly consists of Horner-Emmons reac- tions of carbonyl compounds with sulf…     

Synthesis and photolysis of copolymers with 1-(4-carbethoxyphenyl)-2-propen-1-one structural units

New light-sensitive copolymers containing 1-(4-carbethoxyphenyl)-2-propen-1-one (PCOOEt) chromophore and as comonomer styrene (S), vinyl acetate (VAC), ethyl acrylate (EA), phenyl acrylate (PhA), acrylonitrile (AN) and 1-buten-3-one (MVK) were prepared. Copolymers with MVK were crosslinked. In the copolymerization with VAC, an oligomer with M_GPC about 5000 Dalton and rich in PCOOEt is formed initially. Later, after consumption of PCOOEt, VAC polymerizes to high molecular weight. The oligomers are built in the main chain of VAC. Since the ketone-containing structures are only in the oligomeric part and in the side-chains, no decrease of the molecular weight, as followed by viscometry, was observed during photolysis. Copolymers of PCOOEt with EA, PhA, S and AN degrade under 366 nm irradiation in benzene or dimethylformamide solution with a quantum yield of main chain scission of the same order of magnitude as homopolymer. The quenching of the photolysis of copolymers shows that the reactivity of the triplet state is influenced by the comonomer. A comparison of quenching constants for copolymers with those of homopolymers indicate that self-quenching is not an important deactivation route of the triplet carbonyl group.     

The microwave spectrum of the unsymmetrical conformation of 1-chloro-2-methyl propane

The microwave spectrum of 1-chloro-2-methyl propane has been recorded and lines assigned to ³⁵Cl and ³⁷Cl species in the unsymmetrical conformation. The rotational and distortion constants in MHz are: C₄H₉³⁵Cl, A = 7527.05, B = 2146.21, C = 1793.59, Δ_JK = 4.15 × 10^?3, δ_j = ?8.0 × 10^?5; C₄H₉³⁷Cl, A = 7524.40. B = 2091.73, C = 1755.54, Δ_JK = 2.5 × 10^?3, δ_j = 2.0 × 10^?4.