Conjugated ketones, polymerization

Aryl vinyl ketones are produced thermally from the corresponding quaternary ammonium salts via Hofmann elimination. However, the conjugated ketones are heat-sensitive and polymerization is difficult to avoid. Traditional preparations afforded only moderate yields. Microwave conditions were established for Hofmann eliminations, performed essentially quantitatively, by batch or continuous processes. 

Porri,L. and A. Giarruso, Conjugated Diene Polymerization, Chap. 5 in Comprehensive Polymer Science, Vol. 4, G. C. Eastmond, A. Ledwith, S. Russo, and P. Sigwalt, eds., Pergamon Press, Oxford, 1989. Prabhu, P, A. Shindler, M. H. Theil, and R. D. Gilbert, J. Polym. Sci. Polym. Lett. Ed., 18, 389 (1980). Pregaglia, G. F. andM. Binaghi, Ionic Polymerization of Aldehydes, Ketones, andKetenes, Chap. 3 in The Stereochemistry of Macromolecules, Vol. 2, Marcel Dekker, New York, 1967. 

A polymeric pinacol,poly[3-methyl-2-(4-vinylphenyl)-2,3-butanediol],has been prepared by radical polymerization of the styrenic diol monomer and shown to be cleanly and quantitatively converted to a non-conjugated ketone in the solid state by reaction with a photochemically-generated acid [151,348, 350]. The rearrangement reaction can be readily monitored by IR spectroscopy as the disappearance of the hydroxyl OH absorption is accompanied by appearance of a new ketone carbonyl absorption (Fig. 116). Since a polar alcohol (isopropanol) dissolves the polar diol polymer in the unexposed regions but cannot dissolve the less polar ketone polymer produced in the exposed regions, the resist functions as a negative system with alcohol as a developer. The diol polymer is stable thermally to 225 °C in the absence of acid. 

Mortineau et developed a new initiator to be used with Nd-YAG micro laser for two-photon induced polymerizations. The material is described as a symmetrically conjugated ketone with terminal amino groups. 

Pyrroles react with the conjugate acids of aldehydes and ketones to give carbinols (e.g. 67) which cannot normally be isolated but which undergo proton-catalyzed loss of water to give reactive electrophiles (e.g. 68). Subsequent reaction may lead to polymeric products, but in the case of reaction of pyrrole and acetone a cyclic tetramer (69) is formed in high yield. 

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

Palladium-catalyzed a-arylation of ketones is performed with arylene dihalides and bifunctional aromatic ketones 148 to result in the bond formation at the r/) -a-carbon of the ketone, leading to polyketone 149. The reaction is carried out in the presence of Pd(0) and various phosphines. Several bidentate phosphines and bulky alkylphosphines such as dppf, BINAP, PCys, and P Bu3 are shown to be effective, while PPh3 results in no reaction. Arylene dibromide and diiodide are applicable as the co-monomers. The polymerization reaction is carried out in THE in the presence of NaO Bu at 75 °C under N2, and polymers 149 are isolated in 60-80% yields (M = 7000-15 000). Polyketone 149 is further transformed to conjugated polymer PPV by reduction of the ketone moiety with LiAlH4 followed by dehydration with an acid (Equation (69)). 

In the presence of suitable catalysts, /3-lactones are formed by the action of ketene on aldehydes and ketones. Many catalysts have been used those preferred for aldehydes include boric acid, triacetyl borate, zinc thiocyanate, and zinc chloride. Ketones require stronger catalysts such as boron ttifluoride etherate. The reactions ate conducted at low temperatures (0-10°) to minimize polymerization of the product. Yields of /6-lactones from formaldehyde and acetaldehyde are 85%. The /3-lactones formed from conjugated olefinic ketones decompose to dienoic acids which isomerize to olefinic S-lactones. ... 

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