Partially substituted polyacetylenes

THG measurements on poly- -butylCOT films, referenced to a bare fused silica plate, were made using 1064 nm pulses. These measurements showed that the l/(3)l values of films of poly-rt-butylCOT, lxl0 10 esu, were comparable to that for unoriented polyacetylene at the same wavelength (39). However, comparison of the linear transmission spectra of these materials in the near infrared shows that the partially substituted polyacetylene has greatly improved optical quality. (See Figure 7.)... 

Partially substituted derivatives of polyacetylene are synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) and its derivatives. Certain poly-COT derivatives afford soluble, highly conjugated poly acetylenes. These materials exhibit large third-order optical nonlinearities and low scattering losses. 

In this chapter, we focus on the effect of fluorine as a substituent in a simple polymeric system, polyacetylene. Polyacetylene, of course, has several potentially practical uses because of its conducting and optoelectronic properties (15) and we are interested in studying how F substitution might influence these properties. Our model systems are butadiene and hexatriene, and we discuss both partially fluorinated and perfluorinated materials. Because we discovered that CF - HC hydrogen bonding is important in these systems, we also present results on the nature of the intramolecular hydrogen bond between the CF and OH groups in alcohols and enols. Related results on intramolecular coordination of alkali metals to C-F bonds in fluoroenolates are briefly described. 

The synthesis of enynes is of interest in the chemistry of certain natural products. Terminal enynes occur in several natural products such as histrionicotoxin and laurencin, and the internal enyne unit is found along with polyacetylenes and allenes in natural products from Compositae and Umbelliferae. Both internal Z-and. E-enynes are also useful as precursors to stereochemically define d dienes on their partial reduction. A group from Phillips-Duphar has described an efficient synthesis of the functionalized enyne (95), which serves as the C5 synthon for the convergent synthesis of vitamin A. The l,3-dichloro-2-ether (94) is dechlorinated, substituted, and isomerized in one step on reaction with two molar equivalents of sodium acetylide in liquid ammonia, giving (95) with an E Z ratio... 

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