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Endocyclic alkylation of ketone enolates is shown to depend critically upon the size of the so formed ring and six-but not five-membered cyclic ketones can be synthesized in this way; a rationale for this difference is presented.KETONIC substances of the general type (1) can be deprotonated to the isomeric enolates (2) or (3) which, in principle, may be intramolecularly alkylated (when Y is a leaving group) to the ring structures (4) or ( 5 ) . Since these alkylations proceed by breakage of the enolate double bond in either exocyclic or endocyclic modes, we refer to them as Exo and Endo alkylations, respectively. Recently, in a general treatment of ring closuresJ1s2 we suggested on stereoelectronic grounds that 5-Endo-Trigonal processes, ( 6 ) , were disfavoured, whereas 6-Endo-Trigonal closures, (7), were favoured ring closures. Since the Endo-alkylation,(3) to ( 5 ) , is stereoelectronically similar to the processes (6) and (7) it was possible to predict that the Endo-alkylation of a ketone to a 5-membered ring would be disfavoured, whereas the formation of a 6-membered cyclic ketone, by analogy with the 6-Endo-Trig process (7), in this way would be favoured. We now present evidence that this is true. Thus inverse Markownikov addition of hydrogen bromide to the ketone (8)3 gave (90%) the ketobromide (9), b.p. 130 "C a t 25 mmHg; v (neat) 3000m and 1705s cm-l; 8 (CDCl,) 1.2 (s, 6H), 2.2 (s, 3H), and 2.2 and 3-35 (A,B, m, 4H total), which was converted into both potassium and lithium enolates (10, M = K or Li) with potassium

X-ray absorption edge and extended X-ray absorption fine structure (EXAFS) spectra are reported for the Cu(I) and Cu(II) forms of bovine dopamine beta-hydroxylase (DBH; EC 1.14.17.1) and for the Cu(I) form of DBH bound either to tyramine substrate or to a multisubstrate inhibitor [Kruse, L. I., DeWolf, W. E., Jr., Chambers, P. A., & Goodhart, P. J. (1986) Biochemistry 25, 7271-7278]. A significant change in the structure of the copper sites occurs upon ascorbate-mediated reduction of Cu(II) DBH to the Cu(I) form. While the average Cu(II) site most likely consists of a square-planar array of four (N,O)-containing ligands at 1.98 A, the average Cu(I) site shows a reduction in (N,O) coordination number (from approximately 4 to approximately 2) and the addition of a S-containing ligand at 2.30 A. No change in the average Cu(I) ligand environment accompanies binding of tyramine substrate, whereas binding of a multisubstrate inhibitor, 1-(3,5-difluoro-4-hydroxybenzyl)-1H-imidazole-2(3H)-thione, causes an increase in the Cu-S coordination, consistent with inhibitor binding to the Cu(I) site through the S atom. Although excellent signal-to-noise ratio in the EXAFS spectra of ascorbate-reduced DBH facilitated analysis of outer-shell scattering for a Cu..Cu interaction, the presence of a binuclear site could not be proven or disproven due to interference from Cu...C scattering involving the carbons of imidazole ligands.

The methoxycarbonylation of aryl trifluoromethanesulphonates with CO and aliphatic alcohols is catalysed by P ~( O A C ) ~-~ ,3-bis(diphenylphosphino)propane in high yield at 70 "C and ambient CO pressure.