A new simple and efficient transformation of aromatic aldehydes into α-chlorocinnamaldehydes is described. Catalytic olefination reaction of hydrazones of aromatic aldehydes with 2-trichloromethyl-1,3-dioxolane gives ethylene acetals of target alkenes in moderate to good yields. The reaction proceeds stereoselectively to form preferably Z-isomers.
2-DICHLOROMETHYL-1,3-DIOXOLAN-2-YL ORTHOESTERS. A POTENTIAL PROTECTING GROUP FOR SUGAR DERIVATIVES
作者:H. Özgener、L. Yüceer
DOI:10.1081/car-120016854
日期:——
with acetal protected sugar derivatives in neutral media gave 2-dichloromethyl-1,3-dioxolan-2-yl orthoesters. These orthoesters are readily hydrolysed under mild acidic conditions offering a newmethod for the preparation of readily removable protecting groups. This strategy was realised in the preparation of 6-O-acetyl-3,5-di-O-methyl-1,2-O-isopropylidene-α-d-glucofuranose.
Asymmetric Organocatalyzed Friedel–Crafts Reaction of Trihaloacetaldehydes and Phenols
作者:David Svestka、Jan Otevrel、Pavel Bobal
DOI:10.1002/adsc.202200180
日期:2022.7.5
Herein we report the asymmetric organocatalyzed method for the Friedel–Craftsreaction between activatedphenols and trihaloacetaldehydes. A three-phase screening including 41 compounds was employed to identify a catalyst structure based on 3,5-dinitrobenzamide of 9-amino-epi-cinchonidine as the lead catalytic molecule. Under the optimized reaction conditions, the above catalyst offered trihalohydroxyalkylated