Stereoselective synthesis of substituted dienes by the double ortho ester Claisen rearrangement
作者:Suk-pyo Hong、Sung-jun Yoon、Byung-chan Yu
DOI:10.1016/j.tetlet.2004.12.015
日期:2005.1
This letter shows the highly stereoselective synthesis of substituted (E)-1,3-dienes from substituted propargylic diols via the double ortho ester Claisenrearrangement. The cyclohexyl-substituted diene undergoes thermal Diels–Alder cycloaddition with maleic anhydride to produce the corresponding bicyclic diester in highly stereoselective manner.
Iodine sets allenes ringing: A novel iodine‐promoted tandem cyclization reaction of but‐2‐yne‐1,4‐diol and 4‐aminobut‐2‐yn‐1‐ol derivatives leading to substituted 3,4‐diiodoheterocyclic compounds has been developed (see scheme). In this reaction, a trace amount of water is needed. Both the iodine anion and cation generated from I2 are used in the reaction. The resulting iodides can then be used in
aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I2, IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling
CeCl3-mediated addition of acetylenic bis-lithium salts to aldehydes and ketones: An efficient route to bis-substituted alkyne diols
作者:Jefferson Luiz Princival、Jeiely Gomes Ferreira
DOI:10.1016/j.tetlet.2017.07.094
日期:2017.9
An efficient, chemoselective protocol to access propargylic diols via a CeCl3-mediated addition reaction is reported. Propargylic alcohols were transformed into the corresponding acetylenic bis-lithium salt intermediates, which react with aldehydes and ketones in the presence of dry CeCl3 to furnish the corresponding bis-substituted alkyne diols. This protocol does not involve protection-deprotection