| 摘要 |
1469135 Unsaturated aldehydes INTERNATIONAL FLAVORS & FRAGRANCES Inc 19 July 1974 [30 July 1973 (2)] 32083/74 Heading C2C [Also in Divisions A2 and A5] The invention comprises 2-alkylidene-3-alkenals of formula wherein one of R 1 and R 2 is H and the other is CH 3 and one of R 3 and R 4 is H and the other is C 2 - or C 4 -alkyl and a method of preparing compounds of the above Formula I in which R 1 is C 1-4 alkyl, R 2 is H and one of R 3 and R 4 is C 1-4 alkyl and the other is H, which comprises the steps of (1) reacting an aliphatic alpha-betaunsaturated aldehyde with a halogen to provide the corresponding alpha-halo alkenal where X is halogen; either (i) reacting the said alpha-halo alkenal with an alkyl magnesium halide Grignard reagent, hydrolysing the resulting product to form a hydroxyhaloalkene, and dehydrating the resulting hydroxyhaloalkene to form an alkylidene trans-alkene halide or (ii) reacting the said alpha-halo aldehyde derivative with a tri-substituted alkylidene phosphorane or an alkylidene phosphorus triamide to provide a mixture of alkylidene cis-alkene halide and alkylidene trans-alkene halide; (3) either (i) treating either the mixture of said alkylidene alkene halide isomers or said alkylidene trans-alkene halide with a metal such as magnesium thereby forming an organo-metallic compound where M is MgX and reacting the said organometallic compound so formed with a trialkyl orthoformate (to yield an acetal which is then hydrolysed with acid to yield the desired alkylidene-trans-alkenal or (ii) reacting the mixture of alkylidene alkene halide isomers with an alkyl alkali metal to form a second organometallic reagent (mixture of isomers) of the above formula where M is Li, Na or K and then reacting said organo-metallic reagent with a dialkyl formamide followed by acid hydrolysis forming a mixture of 2-alkylidene-3-cis-alkenal and alkylidene-3-trans-alkenal or (iii) physically separating the alkylidene cis-alkene halide from the alkylidene trans-alkene halide and then reacting each isomer independently with an alkyl alkali metal to form a second organo-metallic reagent and then reacting each of said second organo-metallic reagents with a dialkyl formamide, followed by acid hydrolysis forming, separately, an alkylidene-trans-alkenal and an alkylidene-cis-alkenal, where M is MgX, Li, Na or K and X is halogen. 2-Alkylidene-3-alkenals of the above Formula I, including 2-ciscompounds in R 2 is C 1-4 alkyl and R 1 is H may also be prepared by the processes of Specification 1,468,073. Trans - 2 - ethylidene - cis - 3 - hexenal is also obtained from concentrated orange juice by extraction with ether followed by gas-liquid chromatography. Intermediate compounds isolated in examples of the above-described process are α-chloro- and α - bromo - crotonaldehyde, 3 - chloro - 4 - hydroxy- 2-heptene, 3-bromo- and 3-chloro-2,4-heptadiene. The alkylidene-alkenals are used to modify organoleptic properties, e.g. in foodstuffs, beverages, tobacco and perfumes. |
