Rrans-2-Octenal

Reaction of epichlorohydrin with sodium methanethiolate gave l,3-bis(methylthio)-2-piopanol, which was converted to the sodio derivative and methylated to afford l,3-bis(methylthio)-2-methoxypropane. Finally, treatment with LDA (1 equiv.) resulted in elimination of methanol to give l,3-bis(methyl thio)propene, whereas reaction with 2 equiv. of LDA gave bis(methylthio)allyllithium, which reacted with I bromopentane furnishing l,3-bis(methylthio)-l-octene, which in turn was converted by hydrolysis with mercury(II) chloride to rrans-2-octenal (Scheme 14). 

Moreover, cyclization of(Z)-2-methyl-5-octen-l-ol (3) leads mainly to the 2.5-rran.s-disubstituted tetrahydro-2//-pyran with high 1,4-asymmetric induction and the diequatorial arrangement is preferred81. 

An x-ray structural analysis has been done on thiete 1,1-dioxide (248), naphtho[l,8-bc]thiete 1,1-dioxide (205b),and rrans-2,5-dibromo-7-thiabicyclo-[4.2.0]-l(6)-octene 7,7-dioxide (249). A microwave spectrum of thiete sulfone has been obtained for which an O-S-0 angle of 120.1° was preferred, which differs from the value of 115.5° found in the x-ray analysis. 

Reagents (All reactions were carried out at 155 °C for 24 h in sealed tubes, using C,H, as solvent and a mercurial to carbenophile molar ratio of 1 3, unless stated otherwise.) i, n-CtHii CH CHj (72 h) ii, rrans-Pr CH CHPr iii. MeaSi-CHs CHiCHj (neat) iv, EtaSiH V, cyclohexene vi, cyclo-octene. 

The hydroperoxy epidioxides formed from photosensitized oxidized methyl linoleate are important precursors of volatile compounds, which are similar to those formed from the corresponding monohydroperoxides. Thus, 13-hydroperoxy-10,12-epidioxy-tra 5 -8-enoic acid produces hexanal and methyl lO-oxo-8-decenoate as major volatiles (Figure 4.24). The 9-hydroperoxy-10,12-epidioxy-rrans-13-enoic acid produces 2-heptenal and methyl 9-oxononanoate. Other minor volatile products include two volatiles common to those formed from the monohydroperoxides, pentane and methyl octanoate, and two that are unique, 2-heptanone and 3-octene-2-one. The hydroperoxy epidioxides formed from autoxidized methyl linolenate produce the volatiles expected from the cleavage reactions of linolenate hydroperoxides, and significant amounts of the unique compound 3,5-octadiene-2-one. This vinyl ketone has a low threshold value or minimum detectable level, and may contribute to the flavor impact of fats containing oxidized linolenate (Chapter 5). 

A mixture of acetyl chloride, AICI3, and methylene chloride stirred briefly under Ng, rran -l-hexenylmercuric chloride added, while backflushing with stirred 5 min. rran.y-3-octen-2-one. Y 97%. F. e. s. R. C. Larock and J. C. Bernhardt, Tetrah. Let. 1976, 3097. 

Grieco and coworkers have utilized intramolecular aldolization of keto aldehydes to form seven-mem-bered rings. In a synthesis of ( )-helenalin, keto aldehyde (54) was cyclized to aldol (55 equation 112). - In a later modification of the basic approach, keto aldehyde (56) was cyclized to cycloheptenone (57 equation 113). The success of these cyclizations is related to the fact that the normally preferred five-membered ring closure would yield a strained rrans-fused bicyclo[3.3.0]octene system. 

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