Pentadiene-3-one

The second example is an intermolecular crystal-state reaction. Cross-conjugated 1,5-disubstituted 1,4-dien-3-ones in solution undergo both cis-trans photoisomerization and photodimerization, yielding complex mixtures of products, including die all-trans-substituted cyclobutane 2 in the case of 1,5-diphenyl-1,4-pentadien-3-one. In contrast, dienones such as 3a in whose crystals adjacent molecules lie parallel and strongly overlapped react in the solid to give 3b as the sole photoproduct. This isomerically pure tricyclic diketone results, formally, from an eight-center dimerization. It is not formed in the reaction in solution, and could be prepared by other methods only with considerable difficulty (4). 

An example of the formation of a cyclic product, containing only one sulfur atom, is the reaction of Sx anions with activated double bonds of 1,5 -diphenyl-1,4-pentadiene-3-one yielding in a substituted oxotetrahydrothiopy-ran (Scheme 62) [253]. 

C17H15NO 1,5-diphenyl-l,4-pentadien-3-one oxime Extraction-photometric Cu 61... 

Only three examples of intramolecular organocatalyzed and enantioselective Michael additions of C-nucleophiles seem to have been reported in the literature. In 1979 Wynberg and ten Hoeve reported the (—)-quinine-catalyzed double Michael addition of the 1,3-diones 74a,b to the 1,5-disubstituted pentadien-3-ones 75a-c (Scheme 4.37) [61]. 

Three unique di-diene have been utilized by Meek (9, 10) in the preparation of Diels-Alder copolymers. Reaction of 1,8-diphenyl-octatetraene with ftts-maleimides in refluxing chloroform for several days affords high yields of polymers with softening temperatures well over 300°, but low intrinsic viscosities. The copolymerization of 1,5-di(9-anthryl)-l,4-pentadiene-3-one and anthralazine with fo s-maleimides employs the diene nature of anthracene to obtain polymers with... 

Catalyst Pt/Gc was obtained by carbon monoxide decomposition of the zerovalent R(dpo)2 complex (dpo = 1,5-dlphenyl-1,4-pentadiene-3-one). A suspension of graphite in a CH l2 solution of the complex was stirred while carbon monoxide was bubbling in the solution. After 30 min the slurry was filtered, washed and dried. The platinum loading was 1,1 wt %. 

The iS-oxide 400 undergoes ring-opening, presumably to the sulfenic acid 401, which cyclizes to five-membered products. The intermediate may be trapped by reaction with trimethylsilyl chloride it reacts with norbornene to give bis-norbornyl sulfoxide, probably via an elimination of 2,4-dimethyl-l,4-pentadien-3-one from an initial adduct. 

Tris(dibenzylideneacetone)dipaliadium (0) Palladium, tris(1,5-dipheny 1-1,4-pentadien-3-one)di- (9) (52409-22-0)... 

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