Vinyl ketone, chemical behavior

The chemical behavior of vinyl ketone is in sharp contrast to that of acrylonitrile. No polymerization of AN or methacryl-onitrile (MAN) took place with aluminum alkyl in the absence of Lewis bases. In the presence of HMPT, on the other hand, AN or MAN was polymerized to produce colorless polymers as in the case of vinyl ketone. The last named monomer had to be activated by the coordination of aluminum alkyl, but HMPT, a strong base, took away the aluminum alkyl from the coordination site of vinyl ketone monomer. 

In 2006, the group of Artok showed that 5-aryl-2(5H)-furanones could be prepared in moderate to good yields by a rhodium-catalyzed carbonylative arylation of internal alkynes with aryl boronic acids (Scheme 1.9a) [22]. a,P-Unsaturated ketones (chal-cone derivatives) were formed as the major product when some TFA (trifluoroacetic acid) was added under the same reaction conditions [23a]. By varying the catalytic system, indanones could be produced as the main product [23b]. The chemical behavior of terminal alkynes is different, and either a,P-unsaturated ketones or furans starting from propargylic alcohols can be achieved (Scheme 1.9b) [24, 25]. In the case of vinyl ketones, 1,4-diketones were obtained by rhodium-catalyzed coupling of arylboronic acids in the presence of 20-40 bar of CO [26]. In 2007, Chatani demonstrated that indenones could be accessed by a carbonylative rhodium-catalyzed cyclization of alkynes with 2-bromophenylboronic adds (Scheme 1.9c) [27]. Here, the key intermediate is a vinylrhodium(I) spedes that is formed by transmetaUation of RhCl with 2-bromophenylboronic acid followed by insertion of... 

Most of the conformational properties of the acyl derivatives originate in the high polarity of the C=0 bond. Comparative studies have been reported between several chemical functionalities containing the C=0 moiety, i.e., besides heterocyclic aldehydes and ketones, acyl halides, esters, amides, and urethanes, which have different electronic character. Furthermore, the behavior of the C=0 group has been compared, with regard to its conformational properties, to C=C and C=N double bonds in vinyl derivatives, oximes, and azomethines. Most of the results relative to five-membered aromatic heterocycles have been discussed previously (81RCR336 84KGS579). 

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