Synthons, haloalkenes

Haloalkenes, CH2=CH-(CH2)nX (n = 3-7 X = Cl, Br), are interesting synthons for use in the preparation of long chain alkenols and alkenoic acids 2 in cyclization reactions,3 9 as intermediates in the synthesis of pheromones 10 11 in the preparation of silica gel having a functional surface 12 and for the synthesis of oo-iodochloroalkanes,13 and organogermanium dendrimers.14 They are usually prepared from the corresponding alkenols. 

Haloalkenes are versatile synthons for the synthesis of functionalized olefins and dienes, and are often prepared by the dehydrohalogenation of polyhalo-alkanes. The method often suffers from poor yields or low conversion, but Chin-Hsien has demonstrated that phase-transfer conditions allow the reaction to proceed cleanly, in high yield (79— 90%), ... 

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