Amines phenyl vinyl ketone with

Reaction of phenyl vinyl ketone with cyclopentanone under thermal conditions resulted in a diastereomeric mixture of 1,5,9-triketones 374 via a double Michael reaction. Treatment of this mixture with ammonium formate in polyethyleneglycol-200 under microwave irradiation conditions led to the very fast and efficient formation of a 2 1 diastereomeric mixture of cyclopental flquinolizidines 375 and 376 <2002T2189>. When this reductive amination-cyclization procedure was carried out starting from the purified /ra r-isomer of 374, the result was identical to that obtained from the cis-trans mixture, showing the operation of thermodynamic control (Scheme 86). 

Conversion to phenyl vinyl ketone. Place an intimate mixture of 21.4 g (0.1 mol) of //-dimethylaminopropiophenone hydrochloride and 0.2 g of hydroquinone in a 100-ml round-bottomed flask. Attach a Claisen still-head fitted with a stout capillary air leak and condenser arranged for distillation under reduced pressure place a few crystals of hydroquinone in the receiving flask. Pyrolyse the amine hydrochloride by heating the flask in an electric mantle at 2 mmHg (oil immersion pump), and collect the crude ketone which distils between 70 and 90 °C. On redistillation 7g (51%) of pure phenyl vinyl ketone, b.p. 72-73 °C/3 mmHg (115 °C/18 mmHg), are obtained. Characterise... 

Ozonolysis of vinylpyrazine in methanol at — 30° furnishes pyrazine aldehyde in 73% yield.196 Vinylpyrazine undergoes a variety of addition reactions and pyrazylethyl derivatives of amines, ketones, ethyl phenyl acetate, phenylacetonitrile, and acetamide have been obtained.197-199 2-(2-Pyrazylethyl)cyclohexanone (42) has been prepared both by the condensation of vinylpyrazine with cyclohexanone in the presence of sodium metal and by interaction of vinyl-pyrazine with the pyrrolidine enamine of cyclohexanone followed by hydrolysis.200... 

Carbolithiation reactions of ketone a,-dianions, generated by the above amine-free method with several alkenes, such as styrenyl derivatives, vinyl sulfides and vinylsilanes, can lead to the generation of ketone a,5-dianions (Scheme 15)14. For example, when one equivalents of triphenylvinylsilane was treated with a ketone a,-dianion, in THF, at 0 C for 1 h and the resulting reaction mixture was quenched by 2.2 mol equivalents of trimethylchlorosilane, the corresponding bis-silylated enol silyl ether was obtained. Substituted styrenyl derivatives, such as 1,1-diphenylethylene and cinnamyl alcohol, also underwent a smooth carbolithiation to give the corresponding ketone a,5-dianions. Similar addition reactions of ketone a,f)-dianions to vinyl phenyl sulfide took place smoothly to give a,5-dianions with a sulfur attached in the 5-position. 

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