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Abstract:
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Burgess reagent first prepared by E. M. Burgess in 1968, is a mild
and selective dehydrating agent for secondary and tertiary alcohols and
due to the amphipolar nature it is gainfully employed in a number of
creative synthetic ventures. A close examination of the structure of
Burgess reagent reveals that it can act as a 1,2-dipole. To the best of our
knowledge, no attempts have been made to tap full synthetic potential of
the amphipolar nature of this reagent and no reports on 1,3-dipolar
addition to a σ-bond in acyclic systems are available in literature. In this
context, we propose to unravel novel applications of Burgess reagent
based on its amphipolar nature.
Rich and multifaceted chemistry of nitrones form the basis of
many successful chemical transformations used in attractive synthetic
strategies. For the last 50 years special attention has been given to
nitrones due to their successful application as building blocks in the
synthesis of various natural and biologically active compounds. Our
interest in nitrones stems out of its unique character: i.e. it is a 1,3-dipole
exhibiting distinct nucleophilic activity.
We reasoned that 1,3-dipole possessing significant nucleophilicity
should react with amphipolar Burgess reagent with elimination of
triethylamine to give the corresponding five-membered ring product by
formal dipolar addition to a σ bond. To test this hypothesis we studied
the reaction of nitrones with Burgess reagent. This thesis reveals our
attempts to explore the [3+2] annulation reaction of nitrones with
Burgess reagent which was found to be followed by a rearrangementinvolving C-to-N aryl migration, ultimately resulting in diarylamines and
carbamates.
We have also examined the reaction of cyanuric chloride with
nitrones in DMF with a view to exploit the nucleophilicty of nitrones and
to unravel the migratory aptitude, if any, observed in this reaction |