16509-44-7Relevant 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.
Hydrogenolysis of Small Cycloalkanes, XI. - Hydrogenation of Bicyclobutane-1- and -2-carboxylates
Hertzsch, Winfried,Musso, Hans
, p. 1485 - 1491 (2007/10/02)
Hydrogenation of ethyl bicyclobutane-2-carboxylate (1) with Pd/C in ethanol at normal conditions leads to 95 percent of ethyl 2-methylbutyrate (2) and 5 percent of ethyl n-valerate (3).The corresponding 1-carboxylic acid ester 8 yields 99 percent of 2 but less than 1 percent of cyclobutane as well as the cis- and trans-2-methylcyclopropanecarboxylates 5 and 9.In this case 2-methylenebutyric and cis- and trans-2-methylcrotonic acid esters (10, 11a, and 12) can be detected as intermediates.From these, conclusions can be made about the mechanism at the catalyst. 5 is the main product with a poisoned catalyst.
