Lewis acid catalysis of photochemical reactions. 7. Photodimerization and cross-cycloaddition of cinnamic esters
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 SnCl/sub 4/-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 ..pi.. bonding and net charges. Solid-state photodimerization of free and complexed cinnamic esters and related molecules yield syn head-to-tail (..cap alpha..-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 ester (dimerization) or simple olefin (cross cycloaddition). The catalytic effect of Lewis acids is attributed to an increase in excited-state lifetime and reactivity.
- Research Organization:
- Northwestern Univ., Evanston, IL
- OSTI ID:
- 5522135
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 110:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CINNAMIC ACID
DIMERIZATION
MOLECULAR STRUCTURE
PHOTOCHEMICAL REACTIONS
ESTERS
LEWIS ACIDS
CATALYTIC EFFECTS
BOND LENGTHS
CATALYSIS
CATALYSTS
EXCITED STATES
EXPERIMENTAL DATA
LIFETIME
PHOTOCHEMISTRY
SOLIDS
SOLUTIONS
STEREOCHEMISTRY
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DIMENSIONS
DISPERSIONS
ENERGY LEVELS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
LENGTH
MIXTURES
MONOCARBOXYLIC ACIDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
POLYMERIZATION
400500* - Photochemistry