Showing papers by "George M. Whitesides published in 1973"

Mechanism of reaction of carbon monoxide with phenyllithium

Abstract: The product mixtures obtained by reaction between phenyllithium and carbon monoxide in diethyl ether, followed by hydrolysis, include benzophenone (1). a,a-diphenylacetophenone (2), benzil (3), a,a-diphenyl- a-hydroxyacetophenone (4), benzpinacot (5), a-hydroxyacetophenone (6), 1,3,3-triphenylpropane-1,2-dione (7), 1,3,3-triphenylpropan-1-one-2,3-diol (8). and benzhydrol (9). Compounds 1, 2, 6,7, and 8 are produced in signifi- cant yields i 3,4,5, and 9 are produced in trace quantities. Spectroscopic studies establish dilithium benzophenone dianion (18) as the first long-lived intermediate formed in this reaction; qualitative correlations between the basicity of a number of organolithium reagents and their reactivity toward carbon monoxide suggests, but does not prove, that benzoyllithium is a precursor of 18. Labeling experiments indicate that the products ultimately isolated following hydrolysis of the reaction mixture are derived from at least two pathways which compete for the initially formed 18. One involves combination of l8 with 1 equiv of phenyllithium and 1 equiv of carbon monoxide, followed by elimination of I equiv of lithium oxide. yielding 17, the lithium enolate of 2; a second involves com- bination of 18 with 1 equiv of phenyllithium and 2 equiv of carbon monoxide. yielding 22,the trilithium trianion of 8. Hydrolysis of l7 yields 2 directly. Hydrolysis of 22 yields 8; reverse aldol reactions involving 8 or its pre- cursors generate 1 and 6. The mechanism proposed to account for the major products of the reaction of phenyl- lithium and carbon monoxide is outlined in Scheme III" On the basis of this scheme, plausible paths to the minor products of the reaction are proposed.

Mechanism of interchange of the syn and anti protons of tetra(trihaptoallyl)zirconium(IV)

Abstract: The temperature dependence of the H nmr spectrum of tetra(trihuptoallyl)zirconium(Iv) strates that the syn and anti protons of the allyl moieties interchange. The experimental spectra of the central proton (HI) of the allyl group were compared with line shapes calculated assuming two limiting types of interchange schemes: one (a “concerted” scheme, eq 3) in which interchange occurs simultaneously at the two ends of the allyl group and a second (called a ‘ ‘ u , ~ ” scheme, eq 1) in which interchange occurs at one end of the allyl group at a time. The latter scheme leads to calculated spectra in good agreement with the experimental spectra; the former does not. Calculations performed at several levels of completeness were compared in an effort to identify qualitatively those spectral parameters required to obtain agreement between calculated and observed spectra, in the relatively complex coupled spin system provided by 5 . A very simple classical description utilizing only large coupling constants is capable of describing all of the features of the spectrum qualitatively; however, inclusion of small couplings is required for generation of calculated spectra in quantitative agreement with observed spectra. Although the classical description cannot be used for final spectral refinement, it nonetheless provides a comprehensible picture of the physical processes underlying the dynamic line shape behavior of 5. CFC1, solution demon-

Inversion of configuration in the bromination of vinylic mercurials

Abstract: Aus den definierten Vinylbromiden (I) entstehen uber die Lithio-Verbindungen ′ (II) mit Hg(II)-bromid (III) die Organomercuri-Derivate (IV), die in Schwefelkohlenstoff unter nahezu ausschlieslicher Inversion zu (V) bromiert werden.