3-Hepten-2-one

CONJUGATE ALLYLATION OF a. -UNSATURATED KETONES WITH ALLYLSILANES 4-PHENYL-6-HEPTEH-2-0NE (6-Hepten-2-one, 4-pheny1-)... 

Titanium(IV) is a powerful but selective Lewis acid which can promote the coupling of allylsilanes with carbonyl compounds and derivatives In the presence of titanium tetrachlonde, benzalacetone reacts with allyltnmethylsilane by 1,4-addition to give 4-PHENYL-6-HEPTEN-2-ONE. Similarly, the enol silyl ether of cyclopentanone is coupled with f-pentyl chloride using titanium tetrachlonde to give 2-(tert-PENTYL)CYCLOPENTANONE, an example of a-tert-alkylation of ketones. 

Evidence for de novo synthesis of pheromone components was obtained by showing that labeled acetate and mevalonate were incorporated into ipsdienol by male Ips pini [103,104]. Similarly, labeled acetate and other labeled intermediates were shown to be incorporated into frontalin in a number of Dendroctonus species [105]. Possible precursors to frontalin include 6-methyl-6-hep-ten-2-one, which was incorporated into frontalin by D. ruffipennis [106]. The precursor 6-methyl-6-hepten-2-one also was shown to be converted to bre-vicomin in the bark beetle, Dendroctonus ponderosae [107]. In addition, the expression patterns of HMG-CoA reductase and HMG-CoA synthase are tightly correlated with frontalin production in Dendroctonus jeffreyi [108, 109]. A geranyl diphosphate synthase cDNA from I. pini was also isolated, functionally expressed, and modeled [110]. These data indicate that the de novo isoprenoid biosynthetic pathway is present in bark beetles. A variety of other monoterpene alcohols such as myrcenol, pityol, and sulcitol are probably synthesized through similar pathways [111]... 

The electroreductive cyclization reaction of 6-heptene-2-one 166, producing CIS-1,2-dimethylcyclopentanol 169, was discovered more than twenty years ago [166]. In agreement with Baldwin s rules, the 5-exo product is obtained in a good yield. Since that time, the mechanism of this remarkable regio- and stereoselective reaction has been elucidated by Kariv-Miller et al. [167-169]. Reversible cyclization of the initially formed ketyl radical anion 167 provides either the cis or the trans distonic radical anion. Subsequent electron transfer and protonation from the kinetically preferred 168 leads to the major cis product 169. The thermodynamically preferred 170 is considered as a source of the trace amounts of the trans by-product 171 (Scheme 32). 

Buchwald has reported the titanium-catalyzed cyclization/hydrosilylation of 6-hepten-2-ones and 5-heptenals to form silylated cyclopentanols4 As an example, reaction of 6-hepten-2-one and diphenylsilane catalyzed by Gp2Ti(PMe3)2 in the presence of PMes (O.bequiv.) in toluene at —20°C followed by acidic workup gave... 

Titanium-catalyzed cyclization/hydrosilylation of 6-hepten-2-one was proposed to occur via / -migratory insertion of the G=G bond into the titanium-carbon bond of the 77 -ketone olefin complex c/iatr-lj to form titanacycle cis-ll] (Scheme 16). cr-Bond metathesis of the Ti-O bond of cis- iij with the Si-H bond of the silane followed by G-H reductive elimination would release the silylated cyclopentanol and regenerate the Ti(0) catalyst. Under stoichiometric conditions, each of the steps that converts the enone to the titanacycle is reversible, leading to selective formation of the more stable m-fused metallacycle." For this reason, the diastereoselective cyclization of 6-hepten-2-one under catalytic conditions was proposed to occur via non-selective, reversible formation of 77 -ketotitanium olefin complexes chair-1) and boat-1), followed by preferential cyclization of chair-1) to form cis-11) (Scheme 16). 

C13H22O2, Mr 210.32 is a mixture of isomers, bpo kPa 102 °C, ng 1.4626, a colorless to pale yellow liquid with rosy, spicy, fruity, and woody odor. For its preparation 3,6-dimethyl-6-hepten-2-one and 7-methyl-6-octen-3-one are treated with ethyl diethylphosphoryl acetate to give a mixture of octadienoic acid esters. Cyclization with sulfuric/formic acid yields the title compounds as a mixture with isomers [134]. With its complex odor picture it is used in fine fragrances for shading. 

Sometimes ring closure to form cyclobutanols is favoured. For 6-hepten-2-one (B) in pentane solution the total photoreaction is ... 

Formation of cyclobutanols is closely related to photoelimination.341 For 6-hepten-2-one the total photoreaction in solution is347 ... 

Oxametallacycles are prepared from unsaturated aldehydes or ketones. Oxidative cyclization of 6-hepten-2-one (312) catalysed by the Ti catalyst Cp2Ti to give cyclopentanol 315 has been developed. The key step is the cleavage of the strong Ti—O bond in the oxametallacycle 313 with oxophilic hydrosilane, and the silyl ether 314 is formed with regeneration of Cp2Ti [129,130], Cyclization of 5-hexenal (316)... 

B) Western balsam bark beetle, Dryocoetes confusus formation of endo-brevicomin [(1 F ,5S,7S)-7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1 ]octane] from ( )-6-nonen-2-one (Vanderwel et a/., 1992a) (C) Spruce beetle, Dendroctonus rufipennis formation of frontalin [(1S, 5fl)-(-)-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane] from 6-methyl-6-hepten-2-one (Perez ef a/., 1996 Francke etai, 1995 Francke and Schulz, 1999) (D) European elm bark beetle, Scolytus multistriatus hypothetical formation of oc-multistriatin [(1 S,2F ,4S,5F )-(-)-2,4-dimethyl-5-ethyl-6,8-dioxabicyclo[3.2.1]octane] from 4,6-dimethyl-7-octen-3-one (Francke and Schulz, 1999) and E The colored... 

Phenyl-6-hepten-2-one 6-Hepten-2-one, 4-phenyl- (10) (69492-29-1) Benzalacetone 3-Buten-2-one, 4-phenyl- (8,9) (122-57-6)... 

Kariv-Miller and coworkers have developed indirect electroreductive cyclizations with the dimethyl-pyrrolidinium ion (DMP") as a mediator. Preparative electrolysis of 6-hepten-2-one (9) at a graphite cathode afforded cu-dimethylcyclopentanol (10) in 90% yield (equation 5). The reduction is believed to occur via the ketyl radical anion, which cyclizes onto the alkenic bond. In the absence of DMP simple reduction to 6-hepten-2-ol takes place.Very recently it was shown that instead of DMP several aromatic hydrocarbons can be used as mediators to initiate the cyclization reaction. The carbonyl group can also be cyclized onto an alkynic bond and even an aromatic ring. - ... 

Reduction of 7-octen-2-one mediated by (DMP)Hg5 (DMP" = dimethylpyrrolidi-nium) formed in situ gave the cyclized product with higher current yields (72%) than by direct reduction (35%). Similar results were obtained for 6-hepten-2-one [214]. 

In the case of 6-trimethylsilyl-6-hepten-2-one, the 6-c /n-cyclization product was obtained exclusively, probably due to steric inhibition of 5-cxn-cyclization and electronic effects favoring radical formation in the 6-cwr/o-cyclization [Eq. (43)] [180]. 

Similarly, reduction of 6-heptene-2-one (XI) at Hg in DMF-0.1 M TBA" " yields the alcohol, whereas reduction in the presence of catalytic amounts of DMP yields cis- 2-dimethylcyclopentanol (95%) [90]. The cyclization is suggested to occur at the stage of the radical anion of XI, since in diglyme-0.5% H2O DMP promoted the formation of the pinacol of XI. The cyclization is similar to that described by Shono et al. [91], who reduced XI in MeOH-dioxane at a carbon cathode with 2 M TEA as electrolyte see Chapter 10. 

---