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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.

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Methods for the preparation of l-bromoacetylenes and of mercury acetylides are described.BROMOACETYLENES, RCrCBr, are required for the important Cadiot-Chodkiewicz coupling procedure which is commonly utilised for the synthesis of unsymmetrically substituted conjugated diacetylenic compounds :