Push-pull butadienes

Interesting push-pull dienes, 1-dialkylamino-4-nitro-l,3-butadienes, are prepared by the application of this addition-elimination reaction. (Eq. 4.22).28... 

Fluorinated alkyl cyanides, such as trifluoroacetonitrile, pentafluoropropionitrile, per-fluorobutyronitrile and chlorodifluoroacetonitrile, react with butadiene in the gas phase at 350-400 °C to afford pyridines in high yields (equation 82)72. The push-pull diene 150 and electron-rich cyanides (acetonitrile or acrylonitrile) furnish pyridines (equation 83)73. 

Prokofev et al. (85) studied a number of push-pull butadienes 78 and observed... 

The reaction of 2-formylglycals with malononitrile afforded push-pull butadienes with a sugar moiety. The treatment of these branched-chain sugars with ammonia yielded nicotinonitrile acyclo-C-nucleosides. Furthermore, a one-step ring transformation of 2(3)-formylglycals with Af-aryl-acetoacetanilides gave pyridone acyclo-C-nucleosides [140-142]. 

Benzyl-6-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexofuranos-5-ulose (37) on treatment with carbon disulfide and methyl iodide under basic conditions afforded a-oxoketene dithioacetal 38, which was transformed to pyrazole derivative 39 by exposure to hydrazine hydrate. A 3-deoxy-3,4-unsaturated analogue was similarly prepared. Conversion of ketone 37 to the Knoevenagel product 40 prior to treatment with CS2-MeI-NaH led to the formation of the sugar push-pull-butadiene 41. ... 

The effect of Si02 and Si02-Ti02 surfaces (in the powder form) on the fluorescence and lifetimes of the adsorbed two push-pull stilbenes, , -l-(4-cyanophenyl)-4-(4-N,N-dimethylaminophenyl)-l,3-butadiene and -9-(4-cyanostyryl)-2,3,6,7-tetrahy-dro-lH,5H-pyrido[3,2,l-i,j]-quinoline was observed [56]. The stilbene fluorescence was quenched effectively by mechanism of electron injection from excited stilbene... 

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