3,4-Dimethyl-3-hexen-2-one

The following Lewis acids are also claimed to be superior to AICI3 Zn(Cu)/CH2l2 (AcCl, CH2CI2, A), by which cyclohexene is converted into acetylcyclohexene in 68% yield (after treatment with KOH/MeOH) ZaCh (AcCl, Et20/CH2Cl2, -75 °C -20 °C), by which 2-methyl-2-butene is converted into a 15 85 mixture of 3,4-dimethyl-4-penten-2-one and 4-chloro-3,4-dimethyl-2-pentanone in quantitative combined yield and SnCU. by which cyclohexene (AcCl, CS2, —5 °C — It) is converted into acetylcyclohexene in 50% yield (after dehydrochlorination with PhNEt2 at 180 C), methylcyclo-hexene (CS2, it) is converted into l-acetyl-2-methylcyclohexene in 48% yield (after dehydrochlorination), and camphene is converted into an acetylated derivative in 65% yield. ... 

Ibrning to structurally more complex applications of 100, it has been shown that it can function as a Michael acceptor. For example, when the enolate of 2,4-dimethyl-cyclo-hexen-3-one (152) is treated with 100 in the presence of lithium hexamethyldisilazane (LiHMDS), dichlorovinylation takes place and 153 is formed. On the other hand, with lithium diisopropylamide (LDA) as base, the 1-chloroacetylene derivative 151 is produced [98-100] (Scheme 2-15). The reaction, which also takes place with other 1-chloroacetylenes, most likely involves the Michael intermediate 154 which — depending on reaction conditions — is either protonated or loses a chloride ion. On treatment with copper powder in tetrahydro-furan/acetic acid, 151 is dechlorinated the resulting terminal acetylene has been used for further transformations. 

Sulfones such as allyl-2-methylallyl sulfone and allyl phenyl sulfone and ketones such as 5-hexen-2-one, 2-allyl-2-methyl-l,3-cyclopentanedione, and meth-ylvinyl ketone have been copolymerized.Ethers such as 2,2-dimethyl-4-vinyldioxolane, ° 2-methyl-... 

P-d-Glucopyranosyloxy) -5,6-dihydro-4,6-dimethyl-2H-pyran-2-one. 4-P-d-Glucopyranosyloxy-3-methyl-2-hexen-5-olide... 

Hydrogenation of 2,5-diacetoxy-2,5-dimethyl-3-hexyne 10 over 0% palladium-on-carbon is exceptionally complex. Seven different products are formed together with acetic acid. All are hydrogenolysis products arising from the initially formed 2,5-diacetoxy-2,5-dimethyl-3-hexene 11. One of these, 2,5-dimethyl-2-acetoxy-4-hexene 12 forms in as much as 4S yield. 

Biological. The pure culture Aspergillus niger biodegraded isophorone to 3,5,5-trimethyl-2-cyclo-hexene-l,4-dione, 3,5,5-trimethylcyclohexane-l,4-dione, (5)-4-hydroxy-3,5,5-trimethyl-2-cyclohex-l-one, and 3-hydroxymethyl-5,5-dimethyl-2-cyclohexen-l-one (Mikami et al, 1981). 

To a single-necked, round-bottomed flask equipped with a distillation column are added 2,2-dimethyl-4-hexen-3-ol and one-half its weight of oxalic acid. The mixture is heated so that it slowly distills through the long column. The water layer is separated and the organic layer is dried and distilled to afford a 19% yield of 2,2-dimethyl-3,4-hexadiene, b.p. 107.4°-108.0°C, 5 1.4425, di5 0.7375. 

Those bis(trimethylsiloxy)alkenes resulting in the first step are reactive intermediates which can be converted into a variety of compounds — they give an easy access to many products in a one pot synthesis. For instance via bromination of 3,4-bis(trimethylsiloxy)-3-hexene (303) 2,5-dibromo-3,4-hexadione (307) can be achieved199 whereas l,2-bis(trimethylsiloxy)stilbene (304) yieldsbenzil (308)i99 Simmons-Smith conditions were applied, too, and 2,3-bis(trimethylsiloxy)-2-butene (290) gives l,2-dimethyl-l,2-bis(trimethylsiloxy)cyclopropane (306)2OO ... 

X-ray crystallographic structures of the cw-dioxo osmium(VI) esters derived from dihy-droquinine-4-chlorobcnzoate/Os04/( )-2,2,5,5-tetramethyl-3-hexene and dihydroquinidine 4-chlorobenzoate/Os04/(i )-2,5-dimethyl-3-hexene have also been reported 22. Inspection of these sixteen-electron complexes reveals that, despite the considerable distance between the ligand stereocenters and the reacting site, the 4-chlorobenzoyl moieties effectively shield one of the two possible modes of alkene approach. 

CIC The main flavouring components are alpha-and beta-ionone with their floral, violet and typical perfumy, raspberry, woody character. l-(4-hydroxyphenyl)butan-2-one imparts the fruity, sweet raspberry body. (Z)-3-hexenal is responsible for the fresh, green topnote and 2,5-dimethyl-4 hydroxy-furan-3(2H)-one adds the overripe, almost cooked fruit jammy body. 

CIC The powerful odour is dominated by 2-isobutyl thiazole and 3-pentanethiol. The green notes are lipid degradation products like (E)-2-hexenal, hexanal and higher unsaturated aldehydes, the pineapple-pear like fruity notes are derived from methyl hexanoate, ethyl-2-hexenoate and hexyl acetate. The spicy cinnamon notes are represented by 3-phenyl propyl acetate, cinnamyl acetate, methyl cinnamate, ethyl cinna-mate and ciimamaldehyde. Gamma-decalactone and 2,5-dimethyl-4-hydroxy-furan-3(2H)-one and 3-hydroxy-2-butanone add the sweet, creamy body. Beta-famesene, citronellol, 2-phenylethanol, beta-ionone add the sweet, floral, quincelike part and methyl benzoate and ethyl benzoate impart a characteristic medicinal, exotic topnote. 

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