Probing the Lewis Acid-Catalyzed Intramolecular Diels−Alder Cyclizations of Allylic Alkoxy-Substituted (Z)-1,3-Dienes
摘要:
The Lewis acid-promoted Diels-Aider reaction of (E,Z,E)-trienal 1 provides not only the expected cis-fused cycloadduct 16 but also the transfused products 17 and 18. Trans-fused cycloadducts 17 and 18 are also products of the Lewis acid-promoted cyclization of (E,Z,E)-trienyl acetal 2. These products presumably derive from a stepwise cyclization pathway.
Probing the Lewis Acid-Catalyzed Intramolecular Diels−Alder Cyclizations of Allylic Alkoxy-Substituted (Z)-1,3-Dienes
摘要:
The Lewis acid-promoted Diels-Aider reaction of (E,Z,E)-trienal 1 provides not only the expected cis-fused cycloadduct 16 but also the transfused products 17 and 18. Trans-fused cycloadducts 17 and 18 are also products of the Lewis acid-promoted cyclization of (E,Z,E)-trienyl acetal 2. These products presumably derive from a stepwise cyclization pathway.
Syntheses of Polycyclic Tetrahydrofurans by Cascade Reactions Consisting of Five-Membered Ring Selective Prins Cyclization and Friedel–Crafts Cyclization
homocinnamyl alcohols and aromaticaldehydes with BF3·OEt2 in CH2Cl2 afforded hydrocyclopentafurans. Also hydrocyclopentafurans underwent the same cascade reaction after its furan ring cleavage upon treatment with BF3·OEt2 at roomtemperature. Various combinations of hydropentafurans and aromaticaldehydes or indole aldehydes permitted divergent synthesis of diquinane-furans stuck in aromatic rings.
Total Synthesis of the CP-Molecules (CP-263,114 and CP-225,917, Phomoidrides B and A). 1. Racemic and Asymmetric Synthesis of Bicyclo[4.3.1] Key Building Blocks
作者:K. C. Nicolaou、J. Jung、W. H. Yoon、K. C. Fong、H.-S. Choi、Y. He、Y.-L. Zhong、P. S. Baran
DOI:10.1021/ja012010l
日期:2002.3.1
A brief introduction into the chemistry of the CP-molecules is followed by first-generation synthetic sequences toward key building blocks for their total synthesis. Processes for both racemic and enantiomerically enriched bicyclo[4.3.1] ketone 6 or its equivalent are described, and the absolute stereochemistries of the optically enriched intermediates are determined. The efficient route developed
Oxidation of alkenyl organocuprates formed from alkenyl halides allows the formation of highly substituted symmetrical 1,3-dienes. Cuprates formed from organolithiums and Grignard reagents can be tolerated and the reaction proceeds with retention of alkenyl geometry.