In independent experiments, four carbons in the 4-pentenal skeleton have been labeled with deuterium or methyl and the fate of each label has been determined as the pentenal was transformed into a cyclopentanone derivative by RhCl(PPh3)3(1) at 24-26 °C. The catalyst converted 4-hexenal to 2-methylcyclopentanone (2) in CHC13 and C6H6. Approximately equivalent amounts of hydrocarbon decarbonylation products and RhCl(CO)(PPh3)2 were also formed. 3-Methyl-4-pentenal was isomerized to 3-methylcyclopentanone by 1. 4-Hexenal possessing deuterium at C-2 was isomerized to 2 which contained deuterium at C-5. ínm-4-Hexenal-1 -d was cyclized to 2-3-d and 2-2-d in 9:1 ratio when the reaction was carried to a low conversion. The deuterium in the 2-3-d product was found to be cis to the C-2 CH3 group. ris-4-Hexenal-/-d was isomerized by 1 to afford 2-3-d possessing deuterium trans to the C-2 CH3 group. NMR analyses of these products were assisted by the synthesis and characterization of 2-cis-2,3-d2 by treatment of 2-methylcyclopent-2-en-1 -one with D2 and 1. The 2-cis-2,3-d2 could be converted to a 1:1 mixture of 2-3-d diastereomers on treatment with HC1 in MeOH/H20. The results demonstrated that the cyclization of 4-hexenal-f-rf occurred by a syn addition of the C-D bond to the olefinic bond to generate 2-3-d. The presence of C2H4 in reaction mixtures of 1 and 4-hexenal-1-d resulted in the formation of substantial 2-d0 and C2H3D. The deuterium locations in the 1-pentene, 2-pentene, and ethylcyclopropane decarbonylation products derived from reaction of 4-hexenal-1-d with 1 were determined. The results were interpreted in terms of a hydroacylation mechanism involving an acylrhodium(III) hydride complex and organometallic intermediates derived therefrom. The hydroacylation and decarbonylation products appear to be generated via common intermediates.Acylmetal hydride species have been proposed as possible participants in a group of very important transformations which are promoted by transition metal complexes in solution. These include hydroformylation,1

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Die durch den Rhodium‐Komplex (III) katalysierte Addition von Ethylen (II) an die ungesättigten Aldehyde (I) und (VII) führt zu den ungesättigten Ketonen (IV)‐(VI) bzw. (VIII).

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Die Umsetzung des cis‐Heptenals (I) mit Ethylen (II) in Gegenwart des Rhodium‐Komplexes (III) führt zum cis‐Nonenon (IV).