Chiral Hypervalent Iodine Mediated Enantioselective Phenol and Naphthol Dearomatisation: A Rapid Access to Oxazoline Based Spirocycles

This thesis describes an investigation into the dearomatisation reactions of phenols and naphthols
catalysed by in situ generated hypervalent iodine(III) species, thereby producing a range of spirooxazoline
based compounds in achiral and enantio-enriched forms.

The first part of this dissertation illustrates the synthesis of spiro-oxazolines via oxidative
dearomatisation of phenol and naphthol amides mediated by 4-iodotoluene as catalyst and mCPBA
as terminal oxidant. Different iodoarenes, catalysts, and solvents were scanned, however, 4-
iodotoluene and mCPBA provided the best results in hexafluoroisopropanol (HFIP). It was
observed that altering the oxidant, iodoarene and solvent led to diminished yields in most cases.
The stoichiometric and catalytic versions of the cyclisation were also successfully developed.

The second part of this thesis details the synthesis of novel chiral iodoarenes bearing chiral
appendages. A range of novel iodoarenes possessing chiral ureas, lactates, amides and carbamates
were synthesised in good to excellent yields. The newly synthesised chiral iodoarenes were then
employed and studied in the intramolecular oxidative dearomatisation reactions of naphthol
amides to obtain racemic and chiral oxazoline based spirocycles. A significant increase in the
enantioselectivities was observed when alcoholic solvents were used as additives in
dichloromethane or chloroform at –20 ℃. In the presence of excess alcoholic solvent like ethanol,
methanol and HFIP, poor selectivities were observed.