The First In(OTf)3-Catalyzed Conversion of Kinetically Formed Homoallylic Alcohols into the Thermodynamically Preferred Regioisomers: Application to the Synthesis of 22α-Sterols
摘要:
A retro-ene reaction that generates the parent aldehyde and a sigmatropic rearrangement are involved in the In(OTf)3 -catalyzed conversion of homoallylic alcohols 1 into the thermodynamically favored regioisomers 2. This method can be used for the stereocontrolled synthesis of linear homoallylic 22α-sterols from their readily accessible branched 22β isomers.
One-pot preparation of β-hydroxy esters catalysed by a bis(cyclopentadienyl)titanium(<scp>IV</scp>) dichloride–zinc system
作者:Yu Ding、Gang Zhao
DOI:10.1039/c39920000941
日期:——
The reaction of α-haloesters with carbonyl compounds catalysed by Cp2TiCl2(cat.)–Zn gives β-hydroxyesters.
Cp 2 TiCl 2(cat。)-Zn催化α-卤代酯与羰基化合物的反应,生成β-羟基酯。
A Ball‐Milling‐Enabled Reformatsky Reaction
作者:Qun Cao、Roderick T. Stark、Ian A. Fallis、Duncan L. Browne
DOI:10.1002/cssc.201900886
日期:2019.6.21
An operationally simple one‐jar one‐step mechanochemical Reformatsky reaction using in situ generated organozinc intermediates under neat grinding conditions has been developed. Notable features of this reaction protocol are that it requires no solvent, no inert gases, and no pre‐activation of the bulk zinc source. The developed process is demonstrated to have good substrate scope (39–82 % yield) and
Allylation of Carbonyl Compounds Mediated by Nanometer-Sized Bismuth in Water
作者:Qian Miao、Zhiyong Wang、Xiaolan Xu、Zhenggen Zha
DOI:10.1055/s-2004-822924
日期:——
It is found that nanometer-sized bismuth mediates the allylation of carbonylcompounds in water to afford the corresponding homoallylic alcohol in high yields. Nanometer-sized bismuth is much more effective than regular bismuth powder in this reaction.
Allylation of Carbonyl Compounds Mediated by Aluminum/Fluoride Salts in Water
作者:Shizhen Yuan、Jin Liu、Ling Xu、Shaofeng Zhu
DOI:10.1002/cjoc.201090115
日期:——
A novel mediator (Al/KF) has been developed and employed in the Barbier‐type alkylations of various aldehydes and ketones with alkyl halide in water. The carbonyl compounds could be effectively converted into corresponding homoallylic alcohol in good yields only when allylbromides or substituted allylbromides were used as halides. Aromatic aldehydes could afford homoallylic alcohols in high yields
New and Stereoselective Synthesis of 1,4-Disubstituted Buten-4-ols (Homoallylic Alcohol α-Adducts) from the Corresponding γ-Isomers (3,4-Disubstituted Buten-4-ols) via an Acid-Catalyzed Allyl-Transfer Reaction with Aldehydes
from aldehydes via the usual reaction with common allylic metals 1, were converted to the corresponding α-adducts 6 by an acid-catalyzed allyl-transfer reaction. In the allyl-transfer reaction, anti- and syn-γ-adducts 3 gave E- and Z-α-adducts 6, respectively, and the optical purity of the γ-adducts 3 was transferred to the α-adducts 6 with >98%ee. This suggests that the allyl-transfer reaction proceeds