Syntheses of Substituted 6-Hydroxyhexenoic Acids and Related Tetrahydrofuran Systems by Metallocene-Template Directed 1,4-Selective Coupling of 1,3-Butadiene with Carbonyl Compounds
作者:Gerhard Erker、Martin Berlekamp、Luis Lopez、Matthias Grehl、Bruno Schönecker、Reimar Krieg
DOI:10.1055/s-1994-25441
日期:——
Butadiene is 1,4-selectively coupled with a metal carbonyl and a ketone at the bis(η-cyclopentadienyl)zirconium template to yield the nine-membered metallacyclic products 3. Subsequent hydrolysis under oxidative conditions (pyridine N-oxide) gives the corresponding substituted 6-hydroxy-3-hexenoic acids 5. By this procedure a -CH2CH=CHCH2CO2H nucleophile has thus formally been added to the ketone substrate. Esterification of 5 followed by treatment with a base converts these organic template coupling products into substituted tetrahydrofuran acetic acids. Similarly, ketones are linearly coupled with butadiene and a nitrile to yield analogously structured hydroxyalkenones 15 which undergo acid catalyzed ring closure to yield the -CH2COR substituted tetrahydrofurans 16.
丁二烯在双(δ-环戊二烯基)锆模板上与金属羰基和酮进行 1,4 选择性偶联,生成九元金属环产品 3。随后在氧化条件(吡啶 N-氧化物)下进行水解,得到相应的取代 6-羟基-3-己烯酸 5。通过这一过程,亲核物 -CH2CH=CHCH2CO2H 正式加入到酮底物中。将 5 酯化后再用碱处理,这些有机模板偶联产物就会转化为取代的四氢呋喃乙酸。同样,酮与丁二烯和腈线性偶联,生成结构类似的羟基烯酮 15,经过酸催化闭环,生成-CH2COR 取代的四氢呋喃 16。