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
3-Alkoxyalkanoic esters are directly obtained in high yield from the reaction of acetals with Reformatsky reagents in the presence of titanium(IV) chloride or diethyl ether-boron trifluoride complex in dichloromethane. The reaction of ethyl 4-bromo-2-butenoate is regioselective, affording the product formed by attack on the 4-position. With chiral acetals as substrates, up to 84% enantiomerically enriched 3-hydroxyalkanoic esters can be prepared.
Deprotection of Acetals and Silyl Ethers Using a Polymer-Supported π-Acid Catalyst: Chemoselectivity and Polymer Effect
作者:Nobuyuki Tanaka、Yukio Masaki
DOI:10.1055/s-1999-3000
日期:1999.12
A polymeric dicyanoketene acetal (DCKA), prepared from a styrene monomer bearing dicyanoketene acetal functionality, was found to be an effective and recyclable catalyst in the chemoselective deprotection of acetals and silyl ethers. A remarkable acceleration accountable for the polymer effect was observed.
Anodic Cleavage of Several Ketone <i>N</i>-Phenylsemicarbazones into Methyl <i>N</i>-Phenylcarbamate and the Corresponding Dimethyl Acetals
作者:Shinnosuke Nishikawa、Haruki Yamamori、Kousuke Ohashi、Mitsuhiro Okimoto、Masayuki Hoshi、Takashi Yoshida
DOI:10.1080/00397911.2012.667184
日期:2013.7.3
Abstract Several ketone N-phenylsemicarbazones were electrooxidized in the presence of potassium iodide and a base using methanol as the solvent to give nearly commensurate amounts of methyl N-phenylcarbamate and the corresponding dimethyl acetals. Continuous evolution of gaseous nitrogen was observed from the anolyte during the electrooxidation. The reactions were carried out under very mild reaction
10-Methylacridinium perchlorate (1) effectively promotes various reactions of ketene silyl acetals: aldol and Michael addition products are obtained with aldehydes, ketones, acetals, and α-enones. The reactions exhibit unusual dependency upon 1, namely the yields are excellent when a catalytic amount of 1 is employed whereas no desired products are accessible by the use of 1 in a stoichiometric quantity