Stereoselective routes to conjugated unsaturated compounds from
sec-propargylic alcohols (1) are described. Thermal treatments of β-allenic esters, prepared by the reaction of 1 with trialkyl orthoacetates, with alumina gave (2
E, 4
Z) -alkadienoic esters with high stereoselectivity. β-Allenic amides also rearranged with alumina to give (2
E, 4
Z) -alkadienoic amides. Direct oxidation of 2, 4-alkadienoates with SeO
2 afforded furans and selenophenes. Iodolactonization of, β-allenic acids gave γ-alkylidene butenolide in one step. Stereoselective rearrangements of 2, 4-alkadienoates to 3, 5-alkadienoates with lithium diisopropylamide are described. Application of (2
E 4
Z) -dienoates to the synthesis of natural products such as insect pheromones, flavors, octadecapolyenoic acids and leukotriene A
4 methyl ester are described. Base-catalyzed condensation of
sec-pro-pargylic alcohols with 1-cyanopyrrolidine gave imidates, which undergo thermal rearrangement to give pyridones or dienyl-ureas. Reaction of 1-alkyn-3-ol with benzonitrile gave 4-methylene-4, 5-dihydrooxazoles, which serve as useful intermediates for the synthesis of highly functionalized oxazoles.
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