6- Methyl-2-hepten

Figure 13.10 DEPT-NMR spectra for 6-methyl-5-hepten-2-ol. Part fa) is an ordinary broadband-decoupled spectrum, which shows signals for all eight carbons. Part [b) is a DEPT-90 spectrum, which shows only signals for the two CH carbons. Part (c) is a DEPT-135 spectrum, which shows positive signals for the two CH and three CH3 carbons and negative signals for the two CH2 carbons.

Problem 13.9 Assign a chemical shift to each carbon in 6-methyl-5-hepten-2-ol (Figure 13.10). Problem 13.10 Estimate the chemical shift of each carbon in the following molecule. Predict which... 

Methyl-5-hepten-2-one is a constituent of lemongrass oil. How could you synthesize this substance from methyl 4-oxopentanoate ... 

DEPT-NMR spectrum. 6-methyl-5-hepten-2-ol, 451 Detergent, structure of, 1065 Deuterium isotope effect, 386-387 El reaction and, 392 E2 reaction and, 386-387 Dewar benzene. 1201 Dextromethorphan, structure of, 294 Dextrorotatory, 295 Dextrose, structure of. 973 Dialkylamine, pKa of, 852 Diastereomers, 302-303 kinds of, 310-311 Diastereotopic (NMR), 456... 

N-Methylcyclohexylamine, 13C NMR spectrum of, 954 1H NMR spectrum of, 953 Methylene group, 178 N-Methylguanine, electrostatic potential map of, 1121 6-Methyl-5-hepten-2-ol, DRPT-NMR spectra of. 451... 

By synthesizing pure enantiomers of pheromones, various stereochemistry-pheromone activity relationships could be clarified. For example, in the case of sulcatol (6-methyl-5-hepten-2-ol),both the enantiomers are necessary for bioactivity. For other relationships, please refer to [4-9]. 

Representatives of the subfamilies Omaliinae and Proteininae (omaliine group) possess an abdominal defensive gland reservoir that opens out between sternite 7 and 8 [ 120]. The multi-component mixtures contained in these glands are used for defence. In Omaliinae and Proteininae the secretion is characterized by mixtures of acids (e.g. 2-methylpropanoic acid, hexanoic acid, 2-octenoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, butyric acid, and tiglic acid), aldehydes (( )-2-hexenal, heptanal, octanal, nonanal), ketoaldehydes such as 4-oxo-2-hexenal 41 (Scheme 5), 6-methyl-5-hepten-2-one, alcohols (octanol, ( )-2-hexen-l-ol, 2-methylbutan-l-ol), alkanes (nonadecane), esters (2-methylbutyl tiglate 42, various propanoates, 2-hexenyl 3-methylbutanoate, 2-methylbutyl 2-methylbutanoate, octanoates,butanoates), and aromatic compounds (e.g. 2-phenethyl 3-methylbutanoate 43). Unusual compounds are 2-... 

Adults of the Steninae possess paired eversible abdominal defensive gland reservoirs [119,128]. When the beetles walk on the water surface the spreading secretion propels the beetle forward which represents an unique escape mechanism. The secretion contains isopiperitenole 57,1,8-cineole 58,6-methyl-5-hepten-2-one and the unique spreading alkaloid stenusine, N-ethyl-3-(2-methylbutyl)piperidine 59. Natural stenusine was found to be a mixture of all four stereoisomers in a ratio of (S, S) (S, R) (R, R) (R, S)=43 40 13 4. An enantioselective synthesis of stenusine has been carried out via an Enders-approach [129]. 

Recordings from Staphylininae [115] include 3-methylbutanal, the corresponding alcohol, and its acetate, various ketones such as 4-methyl-3-hexanone, 4-methyl-3-heptanone, 5-methyl-3-hexanone (and the corresponding alcohol), 2-heptanone, 6-methyl-2-heptanone, 6-methyl-5-hepten-2-one as well as methyl-cyclopentene and methylfuran. In addition, the secretions of Ontholestes murinus contain the spiroacetals (2S,6R,8S)-2,8-dimethyl-l,7-dioxaspiro[5,5]-... 

The first suitable representative of this class of substances, 6-methyl-5-heptene-2-one, was investigated by Neuberg and Lewite. This ketone, which is a natural constituent of ethereal oils, can also be obtained by degradation of various aliphatic and cyclic terpenes. By means of fermenting yeast it is converted to 6-methyl-5-heptene-2-ol,... 

Bei der Bestrahlung von 1-Methyl-cyclobuten (25) in Aceton mit Licht der Wellenlange A = 254 m[ji werden nur Carbonyl-Verbindungen isoliert, unter denen das 6-Methyl-5-hepten-2-on (26) das Hauptprodukt darstellt. 

Reagents (i) nBuLi, TMEDA, hexane 0 °C, then 6-methyl-5-heptenal (ii) c.HCI, MeOH, heat, 1h. 

FIGURE 6.28 Oxidation of squalene to 6-methyl-5-hepten-2-one, acetone, geranyl acetone, and 4-oxopentanal (adapted from Fruekilde et al., f998). 

Fruekilde, P J. Hjorth, N. R. Jensen, D. Kotzias, and B Larsen, Ozonolysis at Vegetation Surfaces A Source of Acetone, 4-Oxopentanal, 6-Methyl-5-hepten-2-one, and Geranyl Acetone in the Troposphere, Atmos. Environ., 32, 1893-1902 (1998). 

Grosjean, E., D. Grosjean, and J. H. Seinfeld, Gas-Phase Reaction of Ozone with tra/rx-2-Hexenal, tra/rx-2-Hexenyl Acetate, Eth-ylvinyl Ketone, and 6-Methyl-5-hepten-2-one, Int. J. Chem. Kinet., 28, 373-382 (1996). 

Additional examples are the synthesis of the pheromone (iS )-6-methyl-5-hepten-2-ol (S-sulca-tol) (8)61 and of (/t)-2,3-epoxypropyl butanolate (9)62, which serves as the starting material in the synthesis of the -blocker l-(l-naphthenyloxy)-3-isopropylamino-2-propanol10. 

It is a yellow liquid with a powerful, green, cucumber-like and melon odor. It can be prepared by Darzens reaction of 6-methyl-5-hepten-2-one with ethyl chloroacetate. The intermediate glycidate is saponified and decarboxylated to yield the title compound. 

Since linalool is an important intermediate in the manufacture of vitamin E, several large-scale processes have been developed for its production. Preferred starting materials and/or intermediates are the pinenes and 6-methyl-5-hepten-2-one. Most perfumery-grade linalool is synthetic. 

Addition of acetylene to acetone results in the formation of 2-methyl-3-butyn-2-ol, which is hydrogenated to 2-methyl-3-buten-2-ol in the presence of a palladium catalyst. This product is converted into its acetoacetate derivative with diketene [38] or with ethyl acetoacetate [39]. The acetoacetate undergoes rearrangement when heated (Carroll reaction) to give 6-methyl-5-hepten-2-one ... 

Methyl-5-hepten-2-one is converted into linalool in excellent yield by base-catalyzed ethynylation with acetylene to dehydrolinalool [45]. This is followed by selective hydrogenation of the triple bond to a double bond in the presence of a palladium carbon catalyst. 

Industrial synthesis of nerolidol starts with linalool, which is converted into ger-anylacetone by using diketene, ethyl acetoacetate, or isopropenyl methyl ether, analogous to the synthesis of 6-methyl-5-hepten-2-one from 2-methyl-3-buten-2-ol. Addition of acetylene and partial hydrogenation of the resultant dehydroner-olidol produces a mixture of cis- and trans-nerolidol racemates. 

Synthesis from Dehydrolinalool. Dehydrolinalool is produced on a large scale from 6-methyl-5-hepten-2-one and acetylene and can be isomerized to citral in high yield by a number of catalysts. Preferred catalysts include organic orthovanadates [55], organic trisilyl oxyvanadates [56], and vanadium catalysts with silanols added to the reaction system [57]. 

---