Urea-Functionalized
Self-Assembled Molecular Prism
for Heterogeneous Catalysis in Water
Prodip Howlader
Paramita Das
Ennio Zangrando
Partha Sarathi Mukherjee
10.1021/jacs.5b12237.s004
https://acs.figshare.com/articles/dataset/Urea_Functionalized_Self_Assembled_Molecular_Prism_for_Heterogeneous_Catalysis_in_Water/2072638
Reaction
of a ditopic urea “strut” (<b>L</b><sub><b>1</b></sub>) with <i>cis</i>-(tmen)Pd(NO<sub>3</sub>)<sub>2</sub> yielded a [3+3] self-assembled molecular triangle
(<b>T</b>) [<b>L</b><sub><b>1</b></sub> = 1,4-di(4-pyridylureido)benzene;
tmen = <i>N,N,N′,N′</i>-tetramethylethane-1,2-diamine].
Replacing <i>cis</i>-(tmen)Pd(NO<sub>3</sub>)<sub>2</sub> in the above reaction with an equimolar mixture of Pd(NO<sub>3</sub>)<sub>2</sub> and a clip-type donor (<b>L</b><sub><b>2</b></sub>) yielded a template-free multicomponent 3D trigonal prism
(<b>P</b>) decorated with multiple urea moieties [<b>L</b><sub><b>2</b></sub> = 3,3′-(1<i>H</i>-1,2,4-triazole-3,5-diyl)dipyridine].
This prism (<b>P</b>) was characterized by NMR spectroscopy,
and the structure was confirmed by X-ray crystallography. The <b>P</b> was employed as an effective hydrogen-bond-donor catalyst
for Michael reactions of a series of water-insoluble nitro-olefins
in an aqueous medium. The <b>P</b> showed better catalytic activity
compared to the urea-based ligand <b>L</b><sub><b>1</b></sub> and the triangle <b>T</b>. Moreover, the confined nanospace
of <b>P</b> in addition to large product outlet windows makes
this 3D architecture a perfect molecular vessel to catalyze Diels–Alder
reactions of 9-hydroxymethylanthracene with N-substituted maleimide
in the aqueous medium. The present results demonstrate new observations
on catalytic aqueous Diels–Alder and Michael reactions in heterogeneous
fashion employing a discrete 3D architecture of Pd(II). The prism
was recycled by simple filtration and reused several times without
significant loss of activity.
2016-02-04 19:21:08
prism
Pd
product outlet windows
ci
Diel
medium
urea
NMR
3 D architecture
Michael reactions