パラジウム触媒を用いるβ-ケト酸アリル及びギ酸の新反応とその天然物合成への応用

抄録

Allyl β-keto carboxylates undergo the following four different palladium-catalyzed reactions with high selectivity by selecting reaction conditions. 1. Decarboxylation-allylation to give α-allyl ketones. 2. Decarboxylation-dehydrogenation to give α, β-unsaturated ketones by the reaction in boiling acetonitrile. 3. Decarboxylation-deacetoxylation of α-acetoxylmethyl-β-keto carboxylates to give α-methylene ketones in acetonitrile at room temperature. 4. Decarboxylation-hydrogenolysis to give ketones by the reaction of ammonium formate. Palladium-catalyzed reaction of allylic esters with formic acid-triethylamine gives 1-olefins with high selectivity by using palladium-tributylphosphine as a catalyst. Allylic group can be used as a protecting group of carboxylic acids. Amines are also protected by forming allyl carbamates. They are deprotected by the palladium-catalyzed reaction of formic acid-triethylamine. The formal 3-butenylation of the lactone by Pd-catalyzed alkylation with allylic carbonate followed by hydrogenolysis with ammonium formate was used in the synthesis of optically active steroid C, D-ring and side chain. Moreover, stereoselectivities in methylations of 2, 3-dialkylcyclopentanone enolates derived by the Michael addition to 2-alkylcyclopentanones, obtained by Pd-catalyzed decarboxylation-dehydrogenation, were examined.