A high-dilution modification of the conventional Glaser procedure for the oxidative coupling of ethynyl compounds has been used in the synthesis of new macrocyclic systems containing the ay-diyne unit, notably the hydrocarbons cyclotetradeca-1 : 3-diyne (IIa; n = 10) and cyclooctacosa-1 : 3 : 15 : 17-tetrayne (IIIa; n = lo), and the macrolides (IIb and IIIb).IN a preliminary announcement? we reported the synthesis of a number of macrocyclic compounds containing the ay-diyne unit. The present paper gives a full account of this work and of more recent results. Sondheimer and his collaboratorslb have described independent studies which have also led to cyclic ay-diynes.Medium-sized carbocyclic compounds containing an acetylenic linkage are well known,2 cyclooctyne being the smallest so far obtained. However, at the commencement of these researches, no cyclic ay-diyne had been described, though such compounds would be of particular interest for the study of the correlations of their physical and chemical properties with the degree of ring strain. Further, the presence of other groups within the ring would introduce the possibility of transannular phenomena.
An X-ray diffraction analysis of [W(N2H2)Cl(diphos)2]BPh4 has now been completed. Crystals (methanol) are monoclinic and a = 12.472 (1), b = 19.658 (2), c = 27.056 (3) Á, ß = 92.53 (1)V space group Plxjc, and Z = 4. Independent (5599) reflections with F02 ^3<7(Fo2) (4°^2 ^45°; Mo Ka, graphite monochromator) were observed by the -20 scan routine using an automatic four-circle diffractometer. The structure was solved by conventional heavy-atom techniques. Refinement of positional parameters of all nonhydrogen atoms, of anisotropic temperature factors for W, P, and Cl, and of isotropic Debye factors for the remainder has converged the discrepancy index, Ri, to 0.064. A general view of the structure of the cation and of important bond lengths and bond angles is shown in Figure 1.Our principal concern here is with the geometry of the coordinated N2H2 ligand. The essential linearity
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