Expansion of the applicability of the Truce-Smiles rearrangement
Abstract
The Truce-Smiles rearrangement is a synthetically useful and easily performed reaction
which can be used to condense multiple steps of a synthesis. The nucleophilic aromatic
substitution in this reaction produces a chiral center in the rearrangement product. A variety
of rearrangement substrates has been prepared and investigated. Investigations into tether
functionalization, tether length, pyridyl ring systems and introduction of a second heteroatom
into the tether are reported. It has been shown that the rearrangement prefers nitrile tether
functionalization. For ethyl ester tethers that perform the rearrangement, there is a
secondary cyclization that results in the formation of an aryl lactone. The rearrangement
favours a tether length that proceeds through a 5-membered ring intermediate.
Rearrangement was successfully reported for a substrate which utilizes two heteroatoms in
the tether, something which has not appeared in the literature previously. Use of a
microwave reactor resulted in increased rearrangement yields, in addition to facilitating
rearrangements that were previously unsuccessful using conventional heating with an oil
bath. Use of chiral ionic liquids (CILs) is an excellent approach toward green chemistry due
to their high solubility power, coupled with their ability to be recycled and reused over
multiple reactions. Over recent years, there has been an increasing interest in investigating
the use of CILs as solvent systems to selectively induce chirality in reactions; resulting in
the enantioselective formation of products and reduced waste. A variety of CILs have been
prepared and tested for their ability to serve as solvents and impart chirality on the reaction.
The CILs were successfully used as reaction solvents, however, there is no strong chiral
induction observed.