Date of Award

1-1-1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Rhodium promoted hydroacylations of alkenes by unsaturated aldehydes were investigated. A catalyst derived from 2,4-pentanedionatobis(ethylene)rhodium(I), 31 accomplished the addition of 4-pentenal to ethylene. In a series of experiments the 4-pentenal carbon skeleton was labelled with alkyl groups and deuterium and the fate of each label was determined.Reactions of 4-hexenal, 32, with ethylene in the presence of compound 31 afforded 6-octen-3-one, 33. Experiments were conducted under a variety of conditions and at several different ratios of 32 to 31 to optimize the yield of compound 33. When duroquinone, a free radical inhibitor, was added to the reaction mixture, 2,4-pentanedionatoduroquinonerhodium(I), 36 was formed. Complex 36 failed to react with 32 in the presence of ethylene to give hydroacylation products. The reaction of 32 with (mu),(mu)'-dichlorotetrakis(ethylene)dirhodium(I), 34, afforded 33 as a product. The complex 34, upon treatment with duroquinone, yielded (mu),(mu)'-dichlorobis(duroquinone)dirhodium(I) in a reversible fashion.The fate of the aldehyde hydrogen in the transformation of C(,2)H(,4) + 32 (--->) 33 was determined in experiments employing 4-hexenal-1-d, 32-1-d, as reactant. Treatment of 32-1-d with 31 in CHCl(,3) and CDCl(,3) afforded 33 product possessing > 50% d(,0) molecules while the isotopic composition of recovered unexpended 32 remained > 96% d(,1). The product 33 with an isotopic composition of > 66% d(,0) was afforded when ethylene was introduced to the reaction mixture. The location of deuterium in 33, derived from treatment of 32-1-d with 31 in the absence of added ethylene was determined to be distributed at C-1 and C-2 and the C=C by analysis of ('1)H and ('2)H NMR spectra. Unexpended ethylene was recovered and was found to contain a substantial amount of deuterium. The results were interpreted in terms of a hydroacylation mechanism involving an acylrhodium hydride intermediate. The mechanistic aspects of these results are discussed.

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