Abstract:
Ullman condensation or Ullman C-O arylation is a reaction that uses Cu metal and
thermal conditions to convert aryl halide and phenolic compounds to aryl ethers. The
catalytic performance of silica-based nanoparticles of Cu2O (Cu2O-NP) on Ullmann
C-O arylation was studied by varying the amount and the ratio of Cu2O-NP: silica
combination while keeping the amount of reactants and all other conditions constant.
Iodobenzene and phenol were used as C-O arylation precursors in the presence of Cu2ONP
on silica in DMSO and K2CO3 at the reflux condition. In parallel, we performed the
same reaction under conventional conditions in that the Cu2O-bulk material was used as
the monitoring system. The product formation of the reaction was monitored by using
TLC and gas chromatography methods. Cu2O-NP and supported silica demonstrated
significant catalytic activity in the Ullmann C-O arylation. Among the various ratios
of Cu2O-NP and silica catalysts, maximum yield (52%) of diphenyl ether was obtained
for the catalyst mixture of Cu2O-NP: silica (2:1 W/W) and the Cu2O-NP: iodobenzene
(1:20 mole ratio) while 63% yield of diphenyl ether was obtained in the conventional
method where Cu2O bulk: iodobenzene (1:1 mole) ratio was used. Moreover, with silicabased
Cu2O-NP as the catalyst, the reaction temperature was successfully reduced from
180◦C (conventional method) to 160◦C (with Cu2O-NP and silica). Accordingly, the
Ullman C-O arylation was enhanced economically and environmentally benign manner
with the support of Cu2O-NP and silica.
