Stereoselective Synthesis of (2Z,4E)-2,4-Pentadien-1-ols via Sequential 1,4-Elimination Reaction and [1,2]-Wittig Rearrangement Starting from (E)-4-Alkoxy-2-butenyl Benzoates
摘要:
The sequential 1,4-elimination reaction of (E)-4-alkoxy-2-butenyl benzoates and [1,2]-Wittig rearrangement gave (2Z,4E)-2,4-pentadien-1-ols stereoselectively. Z-Selective formation of intermediary vinyl ethers, whose stereochemistry was well elucidated by the "syn-effect", was achieved by treatment of the 2-butenyl benzoates with KOH in the presence of Pd catalyst. The subsequent [1,2]-Wittg rearrangement by use of n-BuLi proceeded with retention of the stereochemistry of the intermediary vinyl ethers.
Iron carbonyl-mediated homologous Michael reactions of γ-alkoxy alkenones
作者:Tianhao Zhou、James R. Green
DOI:10.1016/0040-4039(93)88068-t
日期:1993.7
Irontetracarbonylcomplexes of γ-benzyloxy-α,β-unsaturated ketones react with several nucleophiles in the presence of Lewis acids to give γ-substitution products. The allyltetracarbonyliron cation intermediates generated allow retention of configuration of the double bond.
Diastereoselective Zinco-Cyclopropanation of Chiral Allylic Alcohols with <i>g</i><i>em</i>-Dizinc Carbenoids
作者:Jean-François Fournier、Simon Mathieu、André B. Charette
DOI:10.1021/ja054328+
日期:2005.9.28
allylic alcohols using gem-dizinc carbenoids is described. The reaction produces three contiguous stereogenic centers, and the resulting chiral cyclopropylzinc derivatives can be trapped with electrophiles with retention of configuration. Simple functional group manipulations lead to the efficient synthesis of orthogonally protected 1,2,3-substitutedcyclopropane derivatives.
Catalytic alkynylation of diverse ketones and aldehydes using nonmetallic benzyltrimethylammonium hydroxide or a basic resin of the hydroxide type in DMSO is described. Aliphatic or alicyclic carbonyl partners gave satisfactory results, whereas aromatic ones afforded products with low yields. When aromatic aldehydes were reacted with phenylacetylene, enones such as chalcone derivatives were obtained in place of ynols. These organobase-catalyzed systems provide a practical nonmetallic protocol for C-C bond formation.