The copper chelate-catalyzed decomposition of o-methoxycarbonyl-α-diazoacetophenone was carried out in benzene. The reaction gave a dimer of a carbonyl ylide intermediate. The intermediate was trapped with dipolarophiles such as trans-dibenzoylethylene, ethyl fumarate, isoprene and dimethyl acetylenedicarboxylate, yielding 1,3-dipolar adducts in a stereospecific and stereoselective manner. Similar results were obtained in the catalytic decomposition of o-(n-butoxycarbonyl)-α-diazoacetophenone. The configuration of adducts and the mechanism of the reaction are discussed.
The first example of the Wolff rearrangement of α-diazocyclobutanone, the title diazo ketone (2), into the three-membered cyclic ketene (4) was observed. The ketene intermediate (4) could be trapped by its reaction with alcohols, aniline, azobenzene, and N-benzylideneaniline to afford 1-alkoxycarbonyl- (5a–c) and 1-phenylcarbamoyl-2,3-bis(diphenylmethylene)cyclopropane (5e), and 1,2-bis(diphenylmethylene)-5,6-diphenyl-5,6-diaza-(9) and 1,2-bis(diphenylmethylene)-5,6-diphenyl-5-azaspiro[2,3]hexan-4-one (10a), respectively. In contrast to the rearrangement, 2 directly reacted with p-benzoquinone and nitrosobenzene, affording the corresponding 1,3-dipolar cycloadducts (14 and 15).
The reaction of α-diazoacetophenone with olefinic compounds, such as vinyl acetate, cis- and trans-stilbenes and cyclohexene, has been studied in the presence of bis(acetylacetonato)copper-(II). The reaction gave the corresponding cyclopropane derivatives, the addition products of benzoylcarbene to the double bond of olefinic compounds in good yields, accompanied by cis-and trans-dibenzoylethylenes, dibenzoylethane or dilactone. Addition of carbene was found to be stereospecific in the cases of cis- and trans-stilbenes. A mechanism has been advanced in which a ketocarbene-metal chelate complex is included as an intermediate of the reaction.
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