Judges have recognised Dr Melen's contribution to the advancements in main group Lewis acid
Withal, substantial work had been done to improve those properties of Ti-based catalysts via increasing of Lewis acid
, expansion of active temperature window, control of initial structure sintering [3-6].
facilitates reuse and recovering the catalys.
Two sorts of hydrogen groups exist: OH with bridging oxygen atoms which acts as Lewis acid
or base, and OH that works as a Bronsted base .
This might be due to a decrease in Lewis acidity of the modified HY catalyst and a decrease in contact probability of Lewis acid
sites with sugar caused by the outer silicalite-1 layer.
In our present study, we have investigated the one-pot multicomponent reactions (MCRs) to prepare aminopyridine derivatives 1-20 using different Lewis acid
catalysts such as Zn[Cl.sub.2], Al[Cl.sub.3], and Fe[Cl.sub.3] using a molar ratio of 1: 2: 3 (aromatic aldehydes: malononitrile: primary amines) where the desired products were obtained in moderate yields.
Changes in the number of Lewis acid
sites occur because of the change in the coordination number of aluminum or oxygen .
Once it was disclosed that the C-F bond of glycosyl fluorides could be activated by a weak Lewis acid
, stannous chloride (A = Sn[Cl.sub.2] in Fig.
Then, optionally, a second activator component and/or Lewis acid
and subsequently the metal complex were added, and the resulting mixture was allowed to stir for an additional 30 minutes.
The 1:1 complex of Lewis acid
(Al[Cl.sub.3])/Lewis base appears to act as a solvent for the polymer/ Lewis acid
complex formed during the reaction, thereby maintaining the polymer in solution or in a reactive gel state.
A number of polymerization variables can be used to tailor the nature of a carbocationic polymerization including temperature, initiator composition, Lewis acid
coinitiator composition and concentration, addition of a Lewis base, Lewis base composition and concentration, and solvent composition.
The most common methods for polyesterification use strong Bronsted or Lewis acid
catalysts, usually using large excess of either carboxylic acid or alcohol monomer in order to achieve high reaction yields (OLAH et al., 1978).