A facile access to spiro furanone skeleton based on Pd(II)-mediated cyclization–carbonylation of propargylic esters

The oxidative cyclization–carbonylation of propargylic esters mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to th...

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Bibliographic Details
Published in:Tetrahedron 2006-03, Vol.62 (11), p.2545-2554
Main Authors: Kato, Keisuke, Nouchi, Hideaki, Ishikura, Keisuke, Takaishi, Satoshi, Motodate, Satoshi, Tanaka, Hikaru, Okudaira, Kazuho, Mochida, Tomoyuki, Nishigaki, Ryuichiro, Shigenobu, Koki, Akita, Hiroyuki
Format: Article
Language:English
Subjects:
3(2 H)-Furanone
Cyclization–carbonylation
Ethisterone
Ethynylestradiol
Mestranol
Orthoester
Palladium
Propargylic ester
Spiro furanone
β-Ketoesters
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Summary:The oxidative cyclization–carbonylation of propargylic esters mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to the alkyne carbon coordinated to palladium(II). When the γ-acetoxy-β-ketoesters were treated with a basic condition, Knoevenagel–Claisen type condensation took place, and spiro furanone derivatives were obtained in good yields. We applied these reactions to steroid derivatives, and steroid derivatives having a spiro furanone fragment were synthesized. Among them, the spiro furanone 4j had vasorelaxant and bradycardiac activities. Compounds 2i– 4k had inhibitory effect on CYP3A. Graphical Abstract
ISSN:0040-4020
1464-5416
DOI:10.1016/j.tet.2005.12.033