Chemoselective deprotection and deprotection with concomitant reduction of 1,3-dioxolanes, acetals and ketals using nickel boride
作者:Jitender M. Khurana、Kiran Dawra、Purnima Sharma
DOI:10.1039/c4ra15404e
日期:——
An efficient and mild methodology for the reductive deprotection of 1,3-dioxolanes, acetals and ketals to the corresponding aldehydes/ketones and also deprotection with concomitant reduction to the corresponding alcohols has been achieved in quantitative yields using nickel boride generated in situ from nickel chloride and sodium borohydride in methanol. The reactions are chemoselective as halo, alkoxy
An efficient SbCl3-metal system for allylation, reduction and acetalization of aldehydes
作者:- Bo Wang Wei、Shi Li-Lan、Huang Yao-Zeng
DOI:10.1016/s0040-4020(01)85467-3
日期:1990.1
allylatlon of aldehydes with allylic halides at room temperature to give high yields of the corresponding homoallylic alcohols with high regio- and chemoselectivity. SbCl3-Al or SbCl3-Zn in DMF-H2O was found to be an efficient reduction system for conversion of aldehydes to alcohols at room temperature in excellent yields. While alcohol was used as solvent instead of DMF-H2o, the acetalization product was
Dimethylboron bromide and diphenylboron bromide. Acetal and ketal cleavage. Cleavage of MEM, MOM, and MTM ethers.
作者:Yvan Quindon、Howard E. Morton、Christiane Yoakim
DOI:10.1016/s0040-4039(00)88238-6
日期:1983.1
A general and efficient procedure for the cleavage of acetals and ketals by the use of dimethylboron bromide or diphenylboron bromide is described. Under similar reaction conditions, MEM, MOM and MTM ethers also react to afford the parent alcohols in excellent yields.
Protection of ketones or aldehydes as 1,3-dioxolane derivatives proceeds within minutes at room temperature in the presence of N-hydroxybenzenesulfonamide, its O-benzyl derivative, or the tosyl analogue, in the absence of strong protonic acids, and in the presence of base (Et3N). Acid-sensitive groups such as O-THP, O-TBS, or N-Boc are unaffected.
Trifluoroethyl alpha-insertion of acetals has been developed. Aromatic, heteroaromatic, and alkenyl acetals react with in situ generated (trifluoromethyl) diazomethane in the presence of antimony(V) chloride to furnish alpha-trifluoromethyl acetals. A stereoselective version of this transformation exploiting the acetal as a chiral auxiliary is also presented.