112459-95-7Relevant academic research and scientific papers
Using non-covalent interactions to direct regioselective 2+2 photocycloaddition within a macrocyclic cavitand
Nguyen, Nga,Clements, Aspen Rae,Pattabiraman, Mahesh
, p. 2433 - 2443 (2016/03/19)
The relative orientation of guests within ternary inclusion complexes is governed by the host-guest and guest-guest supramolecular interactions. Selectivity in 2+2 photocycloaddition between two alkenes included within a macrocyclic cavitand (γ-cyclodextrin) can be controlled using non-covalent interactions. In this manuscript, we report cavitand-mediated control of regioselectivity between alkyl cinnamates using non-covalent interactions. Using this method, we have shown that regioselectivity can be switched completely from a head-to-head dimer to a head-to-tail dimer. The reactions were also stereoselective in most cases. Stoichiometry experiments were performed to explore relative stabilities of the complexes, which indicate that the ternary complex is more stable than others. Selectivity in the photocycloaddition reaction was also applied retrospectively to deduce intermolecular orientations. Time-dependent conversion study we performed indicates that the observed reactivity of alkenes is representative of the intermolecular orientations in the bulk of the complex medium. Experimental observations and computational studies were used to qualitatively understand the complex structures, and relative magnitudes of the weak interactions. The reactions of complexes were studied in slurry form, and the extent of reaction control suggests a solid-state-like behavior.
Lewis Acid Catalysis of Photochemical Reactions. 7. Photodimerization and Cross-Cycloaddition of Cinnamic Esters
Lewis, Frederick D.,Quillen, Suzanne L.,Hale, Paul D.,Oxman, Joe D
, p. 1261 - 1267 (2007/10/02)
The effects of Lewis acid complexation upon the molecular structure, solid-state photodimerization, and solution dimerization and cross-cycloaddition of cinnamic esters have been investigated.Comparison of crystal structures for free and SnCl4-complexed ethyl cinnamate indicates that the enone double bonds are lengthened, the single bonds are shortened, and the enone conformation changes from s-cis to s-trans upon complexation.These changes are consistent with calculated changes in ? bonding and net charges.Solid-state photodimerization of free and complexed cinnamic esters and related molecules yield syn head-to-tail (α-truxillate) dimers.In most cases the Lewis acid complexes dimerize more efficiently and stereoselectively than the free esters.Photodimerization and cross-cycloaddition of methyl cinnamate in dilute solution is also catalyzed by Lewis acids.The mechanism of these reactions involves electronic excitation of a ground-state methyl cinnamate-Lewis acid complex followed by reaction of the excited complex with ground-state ester (dimerization) or simple olefin (cross-cycloaddition).The catalytic effect of Lewis acids is attributed to an increase in excited-state lifetime and reactivity.
