The Photorearrangements of a Naphthobarrelene-like System. Dependence on excited-state spin multiplicity and electronic configuration, and evidence for biradical intermediates. Preliminary communication
✍ Scribed by Martin Demuth; Christopher O. Bender; Slivia E. Braslavsky; Helmut Görner; Ulrich Burger; Walter Amrein; Kurt Schaffner
- Publisher
- John Wiley and Sons
- Year
- 1979
- Tongue
- German
- Weight
- 315 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
8-Benzoyl-9-deuterio-naphtho [ de-2.3.4]bicyclo [3.2.2]nona-2,6,8-triene (1) rearranged quantitatively in a photochemical di-z-methane-type process to 2-, 6-, and 9-deuteriated 1 -benzoyl-naphtho [ de-2.3.4]tricyclo [4.3.0.0239]nona-2, 6-diene (8a-c). The phenylhydroxymethyl analogue 2 underwent a similar regioselective rearrangement to 9a-c. The rearrangement 148a-c is proposed to proceed along three reaction paths evolving from two primary photochemical processes of naphthylvinyl and vinyl-vinyl bonding (1 --f 3 + 6). Evidence for a competition between several paths and involvement of biradical intermediates derives from changes in the isotopomeric composition with temperature, and from laser flash detection (A, , , 353 nm) of a transient. The dependence of the quantum yield for product formation from 1 on excitation wavelength and sensitizer triplet energy leads to the conclusion that reaction to the primary biradicals occurs directly from the S , (n, n*) and T2 (n, z*) states, and that reaction from T, (n, n*) and from S, (n, n") proceed either directly or via T,.