Phototransformations of benzopyranols and related systems. Steady-state and laser flash photolysis studies

Journal Article · Fri Apr 29 04:00:00 EDT 1988 · J. Org. Chem.; (United States)

DOI:https://doi.org/10.1021/jo00244a032· OSTI ID:5992679

Ramaiah, D; Scaria, P M; Cyr, D R; Das, P K; George, M V

The phototransformations of several 4-benzopyranol systems incorporating the 1,2-dibenzoylalkene moiety have been studied for steady-state photolysis, product analysis, and nanosecond laser flash photolysis. Under direct photolysis, prototropic reactions leading to 2-pyranols and/or their methoxy analogues are shown to dominate, presumably through the intermediacy of carbocations produced as a result of photodehydroxylation. No products, e.g., butenoic acid/ester derivatives, attributable to intramolecular phenyl groups migration along the 1,2-di-benzoylalkene moiety, are observed. The laser flash photolysis of 4- and 2-pyranols in benzene or methanol shows the formation of triplets, characterized by unusually short lifetimes (submicrosecond), which testify to the reactive nature of the triplets. In addition, in the case of 2-pyranols, longer-lived transient species characterized by absorptions at long wavelengths (700-800 nm) are observed; these are best assigned as biradicals, produced as a result of ring-opening via triplet-mediated C/sub 2/-O bond cleavage. 29 references, 3 figures, 1 table.

• Research Organization: Indian Institute of Technology, Kanpur
• OSTI ID: 5992679
• Journal Information: J. Org. Chem.; (United States), Journal Name: J. Org. Chem.; (United States) Vol. 53:9; ISSN JOCEA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
AROMATICS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
LASER RADIATION
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS