Phototransformations of bridgehead-disubstituted dibenzobarrelenes. Interesting rearrangements of dibenzosemibullvalene intermediates derived from 9-(Hydroxyalkyl)-10-methoxy-substituted dibenzobarrelenes

Ramaiah, D. ; Kumar, S. A. ; Asokan, C. V. ; Mathew, T. ; Das, S. ; Rath, N. P. ; George, M. V. (1996) Phototransformations of bridgehead-disubstituted dibenzobarrelenes. Interesting rearrangements of dibenzosemibullvalene intermediates derived from 9-(Hydroxyalkyl)-10-methoxy-substituted dibenzobarrelenes Journal of Organic Chemistry, 61 (16). pp. 5468-5473. ISSN 0022-3263

Full text not available from this repository.

Official URL: http://pubs.acs.org/doi/abs/10.1021/jo952046u

Related URL: http://dx.doi.org/10.1021/jo952046u

Abstract

The photochemistry of 11,12-dibenzoyl-9,10-dihydro-9-(hydroxymethyl)-10-methoxy-9,10-ethenoanthracene (7a) and 11,12-dibenzoyl-9,10-dihydro-9-(1-hydroxyethyl)-10-methoxy-9,10-ethenoanthracene (7b) has been studied through steady-state photolysis, product analysis, and laser flash photolysis. Irradiation of 7a in benzene, methanol, or acetone gave 69-72% yields of a dibenzopentalene ketone 11a, arising through a dibenzosemibullvalene precursor. Irradiation of 7b, which exists in equilibrium with its cyclic form 7b', gave a mixture of the dibenzopentalene ketone 11b (41%) and the dibenzopentalenopyran derivative, 16b' (26%). The photochemistry of 11,12-dibenzoyl-9,10-dihydro-9,10-dimethoxy-9,10-ethenoanthracene (17) has been reinvestigated. Irradiation of 17 in benzene and methanol gives a 90% yield of an isomeric pentacyclic product 24, formed through the rearrangement of a dibenzosemibullvalene precursor. Irradiation of 17 in aqueous methanol gives a mixture of the dibenzopentalene ketone 22 (40%) and a pentacyclic methanol adduct 21 (34%). The structures of 7b', 11a,b, 16b', 21, and 24 were confirmed through X-ray crystallographic analysis. The 308 nm laser flash photolysis of 7a,b in benzene results in the formation of their triplets (φT = 0.55-0.76). These triplets possess short lifetimes (0.45-0.75 μs) and are quenched by oxygen, 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy (HTEMPO), ferrocene, and β-carotene at rates in the range (0.26-4.7) × 109 M-1 s-1.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:12449
Deposited On:10 Nov 2010 06:36
Last Modified:31 May 2011 06:59

Repository Staff Only: item control page