1647-12-7Relevant academic research and scientific papers
Lewis Acid Catalysis of Photochemical Reactions. 5. Selective Isomerization of Conjugated Butenoic and Dienoic Esters
Lewis, Frederick D.,Howard, Daniel K.,Barancyk, Steven V.,Oxman, Joe D.
, p. 3016 - 3023 (2007/10/02)
The effects of Lewis and Broensted acids upon the photoisomerization reactions of several conjugated butenoic and dienoic esters have been investigated.Lewis acid inhibit the photochemical deconjugation of α,β- to β,γ-unsaturated butenoic esters and shift the photoequilibrium between E and Z isomers toward the Z isomer.As such, irradiation of E α,β-unsaturated esters in the presence of EtAlCl2 provides a convenient method for the preparation of the thermodynamically less stable Z isomer.Irradiation of methyl (E,E)-2,4-hexadienoate and methyl (E,E)-5-phenyl-2,4-pentadienoate in the absence of added catalysts results in nonselective E,Z isomerization to give mixtures of all four stereoisomers in roughly comparable yields.In the presence of the Broensted acid trifluoroacetic acid, quantitative conversion of methyl 2,4-hexadienoates to methyl 3,4-hexadienoate is observed.The acid serves as a catalyst for the thermal 1,3-hydrogen shift of an allenic enol ester formed via a photochemical 1,5-hydrogen shift of the conjugated esters.Irradiation of the ground-state complexes of the conjugated esters with the Lewis acids EtAlCl2 or BF3 results in selective E,Z isomerization about the α,β-double bond in methyl 2,4-hexadienoate and the γ,δ-double bond in methyl 5-phenyl-2,4-pentadienoate.The mechanistic bases for the observed effects of Lewis acids are selective excitation of the more strongly absorbing E complex and more efficient isomerization of the excited E vs.Z complex.
Conversion of α,β-Unsaturated Esters to Their β,γ-Unsaturated Isomers by Photochemical Deconjugation
Duhaime, Randy M.,Lombardo, Domenic A.,Skinner, Ian A.,Weedon, Alan C.
, p. 873 - 879 (2007/10/02)
It is shown that the α,β-unsaturated esters 1, 2, 4, 5, 6, 16, and 18, which have been reported to be inert to photochemical deconjugation or to undergo the reaction inefficiently, can be converted to their β,γ-unsaturated isomers in good yield if the irradiation is performed in the presence of a catalytic amount of a weak base such as 1,2-dimethylimidazole.It is also shown that addition of catalytic amounts of base can alter the product distribution in cases such as 11, 23, and 26 where more than one isomer can be formed.
Process for preparing olefins by metathesis of cyclic olefins with acyclic olefins
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, (2008/06/13)
A process for preparing esters and halides is disclosed comprising the step of reacting a cyclic olefin having the formula I STR1 wherein R1 and R4 are the same or different from each other and each represents hydrogen, methyl, or ethyl; R2 and R3 are the same or different from each other and each represents hydrogen or alkyl containing 1 to 5 carbon atoms; and n represents a whole number from 2 to 12, with an acyclic olefin having the formula II STR2 wherein R5 represents hydrogen, methyl, ethyl or the group STR3 wherein R12 and R13 are the same or different from each other and each represents hydrogen or alkyl containing 1 to 5 carbon atoms; Y represents halogen; an acyloxy group R14 --CO--O wherein R14 represents alkyl containing 1-12 carbon atoms, phenyl or phenyl alkyl containing 7-12 carbon atoms, or an oxycarbonyl group R15 --O--CO wherein R15 represents alkyl containing 1-12 carbon atoms, phenyl or phenyl alkyl containing 7-12 carbon atoms; p represents a whole number from 1-12 except when Y is an R14 CO--O group wherein p is from 2 to 12. R6 and R7 are the same or different from each other and each represents hydrogen, methyl, or ethyl; R8 and R9 are the same or different from each other and each represents hydrogen or alkyl containing 1 to 5 carbon atoms; X represents halogen; an acyloxy group R10 --CO--O--, wherein R10 represents alkyl containing 1-12 carbon atoms, phenyl, or phenylalkyl containing 7-12 carbon atoms, or an oxycarbonyl group R11 --O--CO, wherein R11 represents alkyl containing 1-12 carbon atoms, phenyl, or phenylalkyl containing 7-12 carbon atoms, m represents a whole number from 1-12 except when X is an R10 --CO--O-- group wherein m is from 2 to 12 in the presence of a catalytic composition comprising a halogen-tungsten salt and a reducing agent which is an organic tin compound.
