2.6- Dimethyl-5-heptenal

From a perfumery point of view, trace ingredients again play an important role in the typical aroma of citroneUa oil. In 1980, IFF chemists isolated and characterized two nonterpenic compounds, melonol (2,6-dimethyl-5-hepten-l-ol [4234-93-9]) and melonal (2,6-dimethyl-5-heptenal [106-72-9]) with interesting green-melon odors (10). Although neither of these had previously been reported in nature, melonal has been a product of commerce for a number of years. 

Choice of THF as the solvent, Me2PhSiH as the hydrosilane, and operation under anhydrous conditions are critical for selective silylformylation of 121 to give 122, whereas these regulations are not necessary in the silylformylation of alkynes. Similar silylformylation is applied to 2-(iV-methylpyrrolidyl)aldehyde (60%), 2-furylaldehyde (90%), 2-thiophenecarboxaldehyde (72%), 2,6-dimethyl-5-heptenal (60%), butanal (60%), 2-methylpropanal (75%), ferrocenecar-boxaldehyde (88%), and phenylacetaldehyde (80%) ... 

Another very interesting example from the same group is the use of Sn-Beta for the synthesis of melonal (2,6-dimethyl-5-hepten-l-al), a fragrance that is produced industrially by a Darzens reaction from 6-methyl-5-hepten-2-one, with ethyl chlor-oacetate as reagent. A novel halogen-free synthesis involves the chemoselective... 

R2 = CH2-CH2-CH=C(CH3)2 2-Acetoxy-2,6-dimethyl-5-heptenal 45% R = R2 = C6Hs 2-Acetoxy-2,2-diphenyl-acetaldehyd 55°... 

After treatment of 2,6-dimethyl-5-heptenal with a boron trifluoride diethyl ether complex at 25 C. 2-isopropenyl-5-methylcyclopentanone is formed16 via a cyclization-[1.2] hydrogen shift sequence. Extensive studies have shown that the nature of the reaction can be influenced by the strength and concentration of the Lewis acid employed17. The appearance of several producLs with different constitutional and configurational characteristics can be explained by a common cationic intermediate (Prins or stepwise cne reaction). The results arc summarized in Table 2. 

Dimethyl-5-heptenal propyleneglycol acetal 1740 N No safety concern... 

Z)-Hept-4-enal. See cis-4-Hepten-1-al 5-Heptenal, 2,6-dimethyl-. See 2,6-Dimethyl-5-heptenal Heptene CAS 592-76-7 UN 2278 (DOT)... 

Meiojei . See Corn (Zea mays) starch Melonal Melonyl. See 2,6-Dimethyl-5-heptenal Meistar T . See Ferrous sulfate heptahydrate Meitatox . See Dodemorph-acetate Meithene -G Meithene -H6051] Meithene -H6410M. See Ethylene/VA copolymer MEMA. See,Methoxyethylmercury acetate MEM-chloride. See 2-Methoxyethoxymethyl chloride... 

Diisobutyl ketone Dill (Anethum graveolens) herb extract 2,6-Dimethyl heptanol-4 2,6-Dimethyl-5-heptenal Dimethyl phenethyl carbinol... 

Dimethyl benzaldehyde Di methyl benzyl carbinol Dimethyl benzyl carbinyl acetate a,a-Dimethylbenzyl isobutyrate 2,6-Dimethyl-5-heptenal 2,6-Dimethyl octanal 3,7-Dimethyl-1-octanol a,a-Dimethylphenethyl butyrate a,a-Di methyl phenethyl formate... 

Dill (Anethum graveolens) seed oil 2,4-Dimethylacetophenone 2,6-Dimethyl-5-heptenal Dodecene-1 Elemi gum Ethyl anthranilate Ethyl butyrate Ethyl cinnamate Ethyl isovalerate Ethyl pelarqonate... 

The reactions of 2,6-dimethyl-5-heptenal (38) indicate that the nature of the reaction can be controlled by variation of the strength and amount of Lewis acid. Treatment of 38 with 1.0 equivalent of Me2AlQ at -78 °C gives primarily 39 as a 4 1 mixture of a-methyl and P-methyl isomers, (in the text 38 -45 refer to the alcohol or caibonyl compound obtained after woikup from the structures shown in Figure 12.) We believe that 39 is formed by a concerted ene reaction or from a 7c-complex such as 4 rather than a zwitterionic intermediate since concerted thermal ene reactions of 1,6-dienes has been shown to give mainly -substituted cyclopentanes. ... 

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