Mild copper-catalyzed N-arylation of azaheterocycles with aryl halides

A highly efficient copper(I)-catalyzed N-arylation of azaheterocycles with various aryl halides is reported. The N-arylation reaction can be carried out using as low as 0.5 mol % of (Cu(I)OTf)₂·PhH and 1.0 mol % of 4,7-dichloro-1,10-phenanthroline as the ligand. Furthermore, cheap and stable copper precursors like Cu(I)I and Cu(II)(OAc)₂·H₂O and the cheap and mild base K₂CO₃ can be used.     

UVB exposure impairs immune responses after hepatitis B vaccination in two different mouse strains

Ultraviolet light exposure can impair immune responses that are not restricted to the exposed skin but is also found at other sites, i.e. systemic immunosuppression. Therefore, we investigated the UV-induced modulating effects on vaccination against hepatitis B in a mouse model. Two different mouse strains, BALB/c and C57B1/ 6, were vaccinated intramuscularly against hepatitis B. Mice were exposed to different doses of ultraviolet B (UVB) for five consecutive days on shaved back skin before the vaccination. Vaccination against hepatitis B induced cellular (delayed-type hypersensitivity [DTH] and lymphocyte stimulation test) as well as humoral immune responses in both mouse strains. The DTH responses in C57BB1/6 mice were statistically significantly higher compared with BALB/c mice. UVB exposure induced a dose-dependent suppression of cellular immunity in both strains of mice. C57B1/6 mice seemed to be more susceptible to this suppression. Anti-hepatitis B surface antibodies (total-Ig) were only marginally suppressed after UVB exposure. IgG2a and interferon-gamma levels, both indicators for Th1 immune response, were suppressed in both mouse strains after UVB exposure. In summary, UVB exposure induced a dose-dependent suppression of both cellular and humoral immune responses after hepatitis B vaccination, although the suppressive effects on humoral immunity were limited to IgG2a production. Susceptibility to UVB-induced immunomodulation depended on the strain of mice and their predilection for developing different T cell responses.     

NMR investigations on Stannabicycloundecanes of the type RSn(CH2CH2CH2)3N

The ¹H, ¹³C, and ¹¹⁹Sn NMR data of seven stannabicycloundecanes of the type RSn(CH₂CH₂CH₂)₃N (1, R = Cl; 2 , R = Br; 3 , R = I; 4 , R = OH; 5 , R = SPh; 6 , R = Me; 7 , R = Sn(CH₂CH₂CH₂)₃N) are reported. From ¹H NMR coalescence data at low temperature the free activation enthalpies for the racemisation of the bicyclo[3.3.3]skeleton were estimated to be 37 ± 1 kJ/mol. They are independent of the substituent R. However, it decreases when the tin atom is replaced by silicon for R = Me.     

The potential energy surface for the [C2H2O]+˙ system: The ketene radical cation [CH2CO]+˙ and its isomers

Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C₂H₂O]^+˙ potential energy surface. Four [C₂H₂O]^+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH₂?C?O]^+˙ (a), and the presently unknown ethynol radical cation, [CH₂?C? OH]^+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH₂]^+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol^?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.     

Isomerization and ring-closing metathesis for the synthesis of 6-, 7- and 8-membered benzo- and pyrido-fused N,N-, N,O- and N,S-heterocycles

An isomerization-ring-closing metathesis (RCM) strategy afforded N-substituted 4H-1,4-benzoxazines from the protected N-allyl-2-(allyloxy)anilines. In addition, RCM was used to synthesize the N-substituted, 8-membered benzo-fused heterocycles from the respective diallyl compounds: 1,2,5,6-tetrahydro-1,6-benzodiazocine, 5,6-dihydro-2H-1,6-benzoxazocine, 5,6,9,10-tetrahydropyrido[2,3-b][1,4]diazocine and 5,6-dihydro-2H-1,6-benzothiazocine 1,1-dioxide. The isomerization-RCM approach also afforded the 7-membered ring system, 2,5-dihydro-1,5-benzothiazepine 1,1-dioxide, from the protected N-allyl-2-(allylsulfonyl)aniline. Furthermore, the structure of 1,6-bis[(4-methylphenyl)sulfonyl]-1,2,5,6-tetrahydro-1,6-benzodiazocine was confirmed by a single crystal X-ray determination.     

Enzymatic Kinetic Resolution of 5-Hydroxy-4-oxa-endo-tricyclo[5.2.1.0(2,6)]dec-8-en-3-ones: A Useful Approach to D-Ring Synthons for Strigol Analogues with Remarkable Stereoselectivity

Racemic 5-hydroxy-4-oxa-endo-tricyclo[5.2.1.0(2,6)]dec-8-en-3-one and its 2-methyl analogue were resolved employing a lipase-catalyzed acetylation reaction. The latter compound thus gave access to a homochiral D-ring synthon for strigolactones. The enzymatic acetylation reaction occurred with a remarkable inversion of configuration at C-5, through which it is possible to achieve a highly efficient asymmetric synthesis of 5-acetoxy-2(5H)-furanone.     

Random field forward interest rate models,market price of risk and their statistics

In this paper we consider discrete time forward interest rate models. In our approach, unlike in the classical Heath–Jarrow–Morton framework, the forward rate curves are driven by a random field. Hence we get a general interest rate structure. Our aim is to give an overview of our results in such a model on the following questions: no-arbitrage conditions, maximum likelihood estimation of the volatility, as well as the joint estimation of the parameters and the asymptotic behaviour of the estimators, relationship with continuous models. Finally we give discussion on the practical problems of the estimation and we show several numerical results on the statistics of such models. This research has been supported by the Hungarian Scientific Research Fund under Grants No. OTKA–F046061/2004 and OTKA–T048544/2005.