949-41-7Relevant academic research and scientific papers
Excited state carbon acid dissociation and competing photoarrangements of 5H-dibenzo[a,c]cycloheptene derivatives
Budac,Wan
, p. 1447 - 1464 (2007/10/03)
Structure reactivity studies of excited singlet state carbon acid dissociation and competing formal di-π-methane rearrangement have been carried out to gain more insights on the photochemistry displayed by these compounds. Photolysis in the presence of ethanolamine resulted in stereoselective deprotonation of the pseudo-axial proton. The results show that excited state carbon acid dissociation is a general reaction of dibenzo and dinaphtho cycloheptenes only if photochemical pathways are not competing.
Excited-state carbon acids: Photochemical C-H bond heterolysis vs formal di-π-methane rearrangement of 5H-dibenzo[a,c]cycloheptene and related compounds
Wan, Peter,Budac, David,Earle, Marion,Shukla, Deepak
, p. 8048 - 8054 (2007/10/02)
The possible excited-state carbon acidity behavior of 5H-dibenzo[a,c]cycloheptene (2) and related compounds has been investigated in aqueous CH3CN solution. In non-basic or aprotic solvents such as CH3CN or cyclohexane, direct photolysis of 2 gave exclusively dibenzonorcaradiene (10) (Φ = 0.087 in CH3CN), via both singlet (initial 1,7-hydrogen shift of the methylene hydrogen, followed by electrocyclic ring closure) and triplet (di-π-methane) pathways. However, in aqueous CH3CN or alcohol solutions, the main deactivational pathway from S1 is C-H bond heterolysis from the methylene 5-position. Thus photolysis of 2 in 70% D2O-CH3CN gave 5-deuterio-5H-dibenzo[a,c]cycloheptene (11) as the major product (Φ = 0.028), in addition to 10 (Φ = 0.010), which was found to arise exclusively via a residual triplet (di-π-methane) pathway. Two related derivatives that are somewhat less rigid (1,2- and 3,4-benzotropilidenes, 7 and 5, respectively) underwent formal di-π-methane rearrangement (via initial 1,7-hydrogen shift) exclusively on photolysis, even in aqueous solution, with no evidence for carbon acid behavior. Fluorescence quenching of 2 by added water in CH3CN solution gave a linear Stern-Volmer plot, with kq = 2.05 × 108 M-1 s-1. The fluorescence emissions of 7 and 5 were not quenched to any observable extent on addition of water to CH3CN solutions of these substrates: quenching of fluorescence by H2O appears to be a useful experimental criterion for testing the possibility of excited-state carbon acid behavior of these substrates.
Approaches to 1H-Cyclopropaphenanthrenes. Eliminations with 1a,9b-Dihydro-1H-cyclopropaphenanthrene Derivatives
Mueller, Paul,Thi, Huong Can Nguyen,Pfyffer, Jean
, p. 855 - 864 (2007/10/02)
Base-induced elimination of the sulfonium salt 2i in the presence of furan affords the addition products 7 and 8, derived from 1H-cyclopropaphenathrene (1) and the isomeric cyclopropene 5a (Scheme 3).Upon oxidation, the selenide 2c yields phenanthrene-9-methanol (9), presumably via 1.No evidence for the intermediate 1 is obtained from sulfoxide pyrolysis with 2e, which leads to products formed by radical pathways (Scheme 5).Reductive elimination of the disulfone 3b gives half-reduction to monosulfone 2g and complete reduction to cyclopropane 2 as well as 9-methylphenanthrene (15), but no evidence for the intermediate 1.
