UNSATURATED MACROCYCLIC COMPOUNDS .58. REACTION OF TRANS-1,4-DIBROMO-2-BUTENE AND TRANS-1,4-DICHLORO-2-BUTENE WITH ETHYNYLMAGNESIUM BROMIDE . SYNTHESIS OF PRECURSORS OF FULLY CONJUGATED 14- 16- 20- AND 26-MEMBERED RING CYCLIC COMPOUNDS

Condensation between trans-1,4-dibromo-2-butene (8) and an excess of ethynylmagnesium bromide (10) gave trans-4-octene-l,7-diyne(14), as well as smaller amounts of trans, trans-4,10-tetradecadiene-1,7,13-triyne (15) and all-trans-4,10,16-eicosatriene-1,7,13,19-tetrayne (16). Similarly, condensation between trans-1,4-dichloro-2-butene (9) and an excess of 10 led to 14 and 15. trans-1-Bromo-2-hexen-5-yne (11) and trans-1-chloro-2-hexen-5-yne (12) are presumably intermediates in these reactions, and these substances were shown to be formed from 8 and 9, respectively, by condensation with no more than 1 molar equiv of 10. Neither 11 nor 12 could be obtained pure, but the corresponding iodide 13 was isolated in the pure state by treatment of crude 12 with sodium iodide. Reaction of the iodide 13 with the bis-Grignard derivative of 15 led to all-trans-4,10,16,22-hexacosatetraene-1,7,13,19,25-pentayne (17). Rearrangement of 14 with potassium t-butoxide readily gave 1,3,5-octatrien-7-yne (18) and a small amount of trans-4-octene-2,6-diyne (20), while similar rearrangement of 15 yielded tetradecahexaenyne(s) (type 22). Substances 14,15,16, and 17 are members of a series of linear 1,4-enynes containing terminal acetylenes, which were expected to give dehydroannulenes by oxidative coupling and subsequent rearrangement. In practice, 14, 15, and 16 have been converted by this method to dehydro[16]-, dehydro[14]-, and dehydro[20]annulenes, respectively, as reported elsewhere (the oxidative coupling of 16 to the cyclic monomer 24 is described in the present paper). Although 17 did not give a dehydro[26]annulene by this method, it has been possible to convert the iodide 13 to a tridehydro[26]annulene by a different route. © 1968, American Chemical Society. All rights reserved.