41117-77-5Relevant articles and documents
Green Photo-Organocatalytic C?H Activation of Aldehydes: Selective Hydroacylation of Electron-Deficient Alkenes
Papadopoulos, Giorgos N.,Voutyritsa, Errika,Kaplaneris, Nikolaos,Kokotos, Christoforos G.
supporting information, p. 1726 - 1731 (2018/02/09)
Selective C?H activation is an area of growing importance. Metal-free C?H activation of branched aldehydes mediating the hydroacylation of electron-deficient alkenes is an attractive transformation, but is limited by selectivity issues, especially in the case of α,α-disubstituted aldehydes. Herein, we report a green, cheap, versatile, and easily reproducible selective hydroacylation of alkenes utilizing phenylglyoxylic acid as the photocatalyst and common household bulbs for irradiation, leading to products in excellent yields and selectivities. The reaction mechanism was also studied to account for the high selectivity.
Radical-chain addition of aldehydes to alkenes catalysed by thiols
Dang, Hai-Shan,Roberts, Brian P.
, p. 67 - 76 (2007/10/03)
Thiols catalyse the radical-chain addition of primary aliphatic aldehydes R1CH2CHO to terminal alkenes H2C=CR2R3 to give ketonic adducts R1CH2C(O)CH2C(H)R2R3 in moderate to good yields.The reaction takes place under mild conditions (dioxane solvent, 60 deg C) and is initiated by di-tert-butyl hyponitrite (TBHN).Thiol catalysis is effective for hydroacylation of electron-rich, -neutral and -deficient alkenes, but is most efficient for addition to electron-rich double bonds.For example, the addition of butanal (2 equiv.) to isopropenyl acetate in the presence of TBHN (2x2.5 molpercent) and methyl thioglycolate (MeO2CCH2SH; 2x5 molpercent) gives the adduct in 80percent yield, whilst a similar reaction in the absence of thiol catalyst affords only an 8percent yield.Other enol acetates, silyl enol ethers, an enol phosphate and butyl vinyl ether react similarly.For comparison, the reaction of butanoyl phenyl selenide with isopropenyl acetate, in the presence of tributyltin hydride and azoisobutyronitrile initiator in benzene at 80 deg C, gives the adduct in only 7percent yield.Methyl thioglycolate is generally the most efficient catalyst for hydroacylation of electron-rich alkenes, whilst tert-dodecanethiol is more effective for addition of aldehydes to electron-deficient alkenes.Triorganosilanethiols also function as catalysts, as does the arenethiol 2,4,6-tris(trifluoromethyl)thiophenol.The role of the thiol is to act as a polarity-reversal catalyst that promotes the overall hydrogen-atom transfer from the aldehyde to the carbon-centred radical produced by addition of the acyl radical to the alkene.Intramolecular hydroacylation is also subject to thiol catalysis and the radical-chain cyclisation of citronellal to a mixture of menthone and isomenthone is effectively promoted in the presence of triphenylsilanethiol.
Pyridazine derivatives useful as components of liquid crystal mixtures
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, (2008/06/13)
Compounds of the formula STR1 wherein B is --C C-- or --CH2 CH2 --, R1 is straight-chain C1 -C12 -alkyl and R2 is straight-chain C1 -C12 -alkyl or straight-chain C1 -C12 -alkoxy, their manufacture and use in liquid crystalline mixtures are described.
