N-heterocyclic carbene catalyzed trifluoromethylation of carbonyl compounds

[reaction: see text]. A novel N-heterocyclic carbene (NHC) catalyzed trifluoromethylation reaction of carbonyl compounds was discovered. Both enolizable and nonenolizable aldehydes and alpha-keto esters undergo facile trifluoromethylation with TMSCF3 at room temperature in the presence of only 0.5-1 mol % of the commercially available NHC (1), providing CF3-substituted alcohols in good yields. Selective trifluoromethylation of aldehydes over ketones can be achieved under NHC catalysis. These conditions are mild and simple and tolerate a variety of functional groups.     

(±)-Seudenol和(±)-Frontalin的简便合成

从易得的油酸出发 ,经关键中间体 2 ,6 庚二酮合成了云杉红翅小蠹集合信息素 (± ) Seudenol (3 甲基 2 环己烯 1 醇 )和南部松小蠹集合信息素 (± ) Frontalin (1 ,5 二甲基 6,8 二氧双环 [3 .2 .1 ]辛烷 )。所合成化合物的结构经IR、MS、1HNMR和13CNMR证实。     

Effect of pressure on the free radical reactions of 2-alkoxytetrahydropyrans

In free radical transformations of 2-methoxy- and 2-ethoxytetrahydropyran initiated bytert-butoxy radicals at 130°C, the relative rate of formation of -valerolactone and valeric acid ester was found to change periodically with increase in the extent of transformation, expressed astert-butyl alcohol (TBA) concentration. The ratio of lactone: ether concentration is determined not by the pressure (up to 1000 MPa) as suggested earlier, but by the amplitudes and phase displacement of the oscillations of the rates of formation of lactone and ester. These results are explained by changes in the physical structure of the solution in proportion to the buildup of reaction products as a result of which the reactivity of the 2-alkoxytetrahydropyranyl radical changes in respect of rupture of the endocyclic and exocyclic C-O bonds.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 822–828, April, 1992.     

Henry condensation under high pressure 2. Effect of aromatic aldehyde type and pressure on the yield of ω-nitrostyrenes and secondary processes

Condensation of aromatic aldehydes (I)-(XX) with EtNO₂ and n-PrNO₂ in AcOH in the presence of AcONH₄ or i-BuNH₂ gives primarily-nitrostyrenes (Ia, b)-(XXa, b) and small quantities of nitriles (Ic)-(XXc), oximes (Id)-(XXd), and ketones (Ie, f)-(XXe, f). The yields of (Ia, b)-(XXa, b) at P=1 atm are higher for acceptor substituents on the aromatic ring whereas at P=10 kbar, they are higher for donor substituents. High pressures suppress the formation of (Ic-f)-(XXc-f) and the Z-isomers of (Ia, b)-(XXa, b). The high pressure technique is especially useful in the preparation of donor-substituted (Ia, b)-(XXa, b) which are intermediates in the synthesis of the psychotropic -phenylethylamines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 426–433, February, 1991.     

Lewis acid initiated or high pressure promoted reactions of isoprene with phenylsulphinyl chloride

Lewis acid initiated reaction of isoprene with PhSOCl proceeds in a ene fashion with the formation of 2-phenylsulphinylmethyl-1,3-butadiene. High pressure promoted addition produces Z-1-phenylsulphinyl-4-chloroadduct presumably $\text{via}$ [4+2]cycloaddition.     

Change in the reactivity of di-tert-butyl peroxide during homolysis with an increase in the degree of conversion and pressure

It was found that the differential reactivity (k _d ) of di-tert-butyl peroxide (DTBP) in a solution of 2-methoxy-(1) and 2-ethoxytetrahydropyran (2) at 130°C and pressuresp=20 and 1000 MPa is a periodic function of the degree of conversion, arbitrarily measured by the concentration oftert-butyl alcohol (TBA) formed. The functionk _d =F([TBA]) was calculated with the spline approximation (SA) of the experimental [TBA] as a function of the reaction time , giving a continuous curve of d[TBA]/d as a function of . The integral reactivityk _d =G([TBA]) calculated with the kinetic equation for a first-order reaction for decomposition of DTBP in1, 2, 1 + C ₆ H ₆ and2 + C ₆ H ₆ in three segments of in the range ofp=20–1000 MPa changes differently with an increase in the degree of conversion for differentp. The volume activation effects ( ) determined by SA of the experimental lnk _d as a function ofp were calculated for close degrees of conversion, [TBA]=0.1–0.14M. The as a function ofp obtained were compared with the similarly processed published data on decomposition of DTBP inn-heptane and dicumyl peroxide (DCP) in different aromatic solvents. The results were attributed to the effect of the type of packing of the solvent molecules surrounding the reacting molecule on the reactivity of the peroxide and not to the effect of radical recombination in the primary cage.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 829–837, April, 1992.     

The effects of slippage and diffraction in long wavelength operation of a free electron laser

The Free-Electron Laser user facility FELIX produces picosecond optical pulses in the wavelength range of 5–110m. The proposed installation of a new undulator with a larger magnetic period would allow extension towards considerably longer wavelengths. This would result in the production of extremely short, far-infrared pulses, with a duration of a single optical period or even less. In order to investigate the pulse propagation for free-electron lasers operating in the long wavelength limit, a three-dimensional simulation code was developed. Using the FELIX parameters, with the addition of a long-period undulator, the effects of slippage, diffraction losses, changes in the filling factor, as well as the effects of the optical cavity geometry were studied for wavelengths up to 300m, with electron pulses in the ps regime. It is shown that slippage effects are less restrictive for long wavelength operation than the increasing losses due to optical beam diffraction.     

N-heterocyclic carbene-catalyzed Mukaiyama aldol reactions

N-Heterocyclic carbenes were shown to be highly effective catalysts to promote Mukaiyama aldol reactions. In the presence of only 0.5 mol % of N-heterocyclic carbene (5), various aldehydes and 2,2,2-trifluoroacetophenone underwent Mukaiyama aldol reactions in THF with trimethylsilyl ketene acetal (2) at 23 degrees C as well as with trimethylsilyl enol ether (7) at 0 degrees C to afford aldol adducts in good yields. These conditions are extremely mild and operationally simple and tolerate various functional groups. [reaction: see text]     

Trifluoromethyl ketones from enolizable carboxylic acids via enediolate trifluoroacetylation/decarboxylation

Primary and secondary (enolizable) carboxylic acids were converted in a single step to trifluoromethyl ketones. Treatment of the acid with 2.2 equiv of LDA generated an enediolate that was trifluoroacetylated with EtO(2)CCF(3). Quenching the reaction mixture with aqueous HCl resulted in rapid decarboxylation and provided the trifluoromethyl ketone product in good yield. The process may be performed at -20 degrees C with a slight reduction in yield. The reaction was extended to the preparation of pentafluoroethyl and chlorodifluoromethyl ketones.