Showing papers on "Intramolecular reaction published in 1980"
TL;DR: The relative efficiencies of the twoprocesses are largely predictable and this combined with reasonable chemical and quantum yields make these photoreactions realistic synthetic procedures towards bicyclo[4.2.2] and tricyclo[3.3.0] octane systems as discussed by the authors.
Abstract: Dienophilic ethylenes yield solely ortho photocycloadducts with benzene whereas alkenes and enol ethers give products arising from both ortho and meta cycloaddition. The relative efficiencies of the twoprocesses are largely predictable and this combined with reasonable chemical and quantum yields make these photoreactions realistic synthetic procedures towards bicyclo[4.2.Oloctane and tricyclo[3.3.0.02'8]octane systems. The ortho cycloaddition involves a measure of charge—transfer to or from the ethylene at some stage in the reaction pathway, whereas two routes are considered to account for the orientational selectivity of the meta process involving ethylenes and substituted benzenes. Positions and modes of intramolecular reaction between the chromophores of non-conjugated phenyl vinyl bichromophoric systems are understandable in terms of their favoured molecular conformations leading to preferred orientations of the addends.
57 citations
TL;DR: The rate of alkyl-aryl bond breakage depends on the Bronsted acidity of the active catalyst (e.g. H + (ZnCl 2 X ) − or H+ (AlCl 3 X )− ).
40 citations
TL;DR: In this article, the cis-disubstituted cyclohexene compound reacts only sluggishly to produce a mixture of the cis and trans-fused octalones, affording stereospecific effect of the allylic double bond configuration on the ease of cyclization.
Abstract: The title reaction of trans-3-acetoxy-4-(4-methyl-3-trimethylsiloxy-3-pentenyl)cyclohexene proceeds in the presence of Et2AlOAr, where Ar=2,6-di-t-butyl-4-methylphenyl, affording stereospecifically the cis isomer of 2,2-dimethylbicyclo[4.4.0]dec-9-en-3-one. In contrast, the cis-disubstituted cyclohexene compound reacts only sluggishly to produce a mixture of the cis- and trans-fused octalones. Similar stereospecific effect of the allylic double bond configuration on the ease of cyclization has been observed in the synthesis of karahanaenone from 3,7-dimethyl-6-trimethylsiloxy-2,6-octadienyl acetate and related reactions.
17 citations
1 citations
Abstract: The title reaction of trans-3-acetoxy-4-(4-methyl-3-trimethylsiloxy-3-pentenyl)cyclohexene proceeds in the presence of Et2AlOAr, where Ar=2,6-di-t-butyl-4-methylphenyl, affording stereospecifically the cis isomer of 2,2-dimethylbicyclo[4.4.0]dec-9-en-3-one. In contrast, the cis-disubstituted cyclohexene compound reacts only sluggishly to produce a mixture of the cis- and trans-fused octalones. Similar stereospecific effect of the allylic double bond configuration on the ease of cyclization has been observed in the synthesis of karahanaenone from 3,7-dimethyl-6-trimethylsiloxy-2,6-octadienyl acetate and related reactions.
1 citations