Lewis acid catalysis of photochemical reactions. 7. Photodimerization and cross-cycloaddition of cinnamic esters

Journal Article · Wed Feb 17 04:00:00 EST 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00212a039· OSTI ID:5522135

Lewis, F D; Quillen, S L; Hale, P D; Oxman, J D

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), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:4; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
BOND LENGTHS
CARBOXYLIC ACIDS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CINNAMIC ACID
DATA
DIMENSIONS
DIMERIZATION
DISPERSIONS
ENERGY LEVELS
ESTERS
EXCITED STATES
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
LENGTH
LEWIS ACIDS
LIFETIME
MIXTURES
MOLECULAR STRUCTURE
MONOCARBOXYLIC ACIDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
POLYMERIZATION
SOLIDS
SOLUTIONS
STEREOCHEMISTRY