Unsaturated methyl ketone

Exchange of the butyl vinyl ether for 2-hydroxyethyl vinyl ether enabled the facile transformation of vinyl triflates or bromides into protected a,/i-unsaturated methyl ketones (Eq. 11.14) [27]. One interesting aspect of this reaction is that a masked methyl ketone can easily be introduced into a structure even in the presence of other free ketone groups. 

Male red-sided garter snakes court larger females more than small ones. Even the skin lipid extracts from large females elicit courtship from more males than those from small females. Larger females possess more unsaturated methyl ketones, while small females have more saturated methyl ketones (LeMaster and Mason, 2002). 

Red-sided garter snakes from different regions of Manitoba, Canada show signs of isolation by chemical cues. In choice tests, males from a hiber-naculum (overwintering den) in central Manitoba preferred females from their own population to females from western Manitoba. Males from western Manitoba showed no preference. When confronted with experimental trails, males made the same choices. This demonstrated that a chemical factor is involved. Furthermore, the sexual attractiveness pheromone of females, a series of ty-9-cis-unsaturated methyl ketones, varies between the populations. Specifically, the... 

Similarly, the [3-1-4] annulation of the E- and Z-isomers of /3-hetero-substituted acryloylsilanes 52 with lithium enolates of a,-unsaturated methyl ketones 54 gave stereospecifically the c -6,7-cyclopentyl-5-trimethylsilyl-3-cycloheptenone 55 (equation 20). The stereospecificity in the annulation was explained by an anionic oxy-Cope isomerization of the 1,2-divinylcyclopropanediol intermediate 56, which was generated through the Brook isomerization of the initial 1,2-adduct (equation 20). 

For the puiposes of retrosynthetic analysis, a six-membered ring in a target can be related to a Robinson annulation of an existing ketone with an a,/3-unsamrated ketone. Normally cc,/3-unsaturated methyl ketones are used to facilitate the ring closure, but this is not an absolute requirement. Thus the target steroid S could potentially be constructed by a series of Robinson annulations as shown. The last retrosynthetic step (the first synthetic step) could be problematic as a mixture of regioisomers would be formed. 

Wittig-type reactions.1 In contrast to the corresponding phosphorane reagent, 1 reacts with ketones as well as aldehydes to form a, 3-unsaturated methyl ketones. Two typical products and the yields are formulated. 

Besides chalcones, other types of a,p-unsaturated carbonyls affording five-membered S-heterocycles were cinnamaldehyde, 12, and the a,p-unsaturated methyl ketone 13 and phenyl ketones 14 and 15. However, another phenyl ketone, 16, substituted at the a position or tertiary butyl ketone 17 failed to yield S-heterocycles. 

Saturated methyl ketones Mono unsaturated methyl ketones ... 

Annulation Using (P-(Trimethylsilyl)acryloyl)silane and Lithium Enolate of a,p-Unsaturated Methyl Ketone ... 

Vinylketene thioacetals react by a Michael-type addition with an alkyllithium in THF at -80 to —20°. Thus successive addition of n-butyllilhium and methyl iodide to (8) gives the thioacetal of thea,/i-unsaturated methyl ketone (9) in almost quantitative... 

The readily prepared and air-stable complex trans 4, catalyzes Diels-Alder reactions between 1,3-dienes and a,]3-unsaturated methyl ketones or enals. Nitro-methane is the best solvent, and rate accelerations are up to a factor of 10 compared to the uncatalyzed reaction and up to 10 compared to catalysis by trifluoroacetic acid (Scheme 10.20) [34]. 

The reaction is applicable to saturated and unsaturated methyl ketones of the aliphatic and alicyclic series, to aryl methyl ketones, and to methyl ketones of heterocyclic aromatic compounds. 

Oxidation of VI with chromium trioxide in acetic acid gave a methyl keto ester VII from which benzoic acid was eliminated under mild conditions to give an a,j8-unsaturated methyl ketone. When air was bubbled into an alkaline solution of the a,j8-unsaturated ketone it was... 

New routes to camphenilone and dehydrocamphene derivatives using alkenes614 or allenic esters as dienophiles in Diels-Alder reactions515 have been developed. Lewis acid-catalysed coupling of a,0-unsaturated methyl ketones with cyclo-pentadiene favoured exo-products except when TiCl4 was used,516 and led to isocamphanes that were spasmolytics.517 The tricyclene (214) could be converted... 

Reaction with trialkylboranes. 3-Butyne-2-one, like acrolein (this volume), does not react spontaneously with trialkylboranes, but in the presence of catalytic amounts of oxygen it reacts readily to give a,/3-unsaturated methyl ketones (2)... 

Reaction of a variety of unsaturated methyl ketones with relatively unhindered bromo esters in refluxing ether gave only 1,2-addition products (equation 21). A similar study in refluxing THF with the more hindered ethyl a-bromoisobutyrate gave exclusively 1,4-addition products however, the conditions of work-up were such that 1,2-addition products would not have been isolated (equation 22). ... 

The Carroll rearrangement, an old and well-established thermal rearrangement, involves the rearrangement of allyllc esters to B keto acids followed by decarboxylation to provide y,6-unsaturated methyl ketones. Even though the Carroll rearrangement fs a versatile complement to the Claisen rearrangement, It is not of widespread use. This may be due to (a) the... 

ANNULATION USING A [13-(TRIMETHYLSILYL)ACRYLOYL]SILANE AND THE LITHIUM ENOLATE OF AN a,(3-UNSATURATED METHYL KETONE (1R. 6S. 7S )-4-(tert-BUTYLDI-METHYLSILOXY)-6-(TRIMETHYLSILYL)-BICYCLO[5.4.01UNDEC-4-EN-2-ONE... 

Unsaturated acids can also be obtained in this way, by hypohalite oxidation of a,/ -unsaturated methyl ketones 3-methyl-2-butenoic acid has thus been obtained from mesityl oxide,136 and 5-phenyl-2,4-pentadienoic acid in 70% yield from cinnamylideneacetone 137... 

REDUCTION OF THE CC-DOUBLE BOND OF a,B-UNSATURATED CARBOXYLATES, ALDEHYDES OR a,B-UNSATURATED METHYL KETONES. 

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