Novel cascade aryne-capture/rearrangement reactions

Arynes are reactive intermediates that have been an academic curiosity for over a century. A recent renaissance of interest in the chemistry of these intermediates can be traced back to the development of ortho-(silyl)aryl triflates as aryne precursors. The application of aryne chemistry outside academia has been precluded by the expense and laborious preparation of these precursors. Diphenyliodonium-2-carboxylate has been shown to be a stable and inexpensive benzyne precursor, however application has been limited due to the high temperature (>160 ºC) and long reaction times required to generate benzyne by this protocol. Described within is an investigation whereby diphenyliodonium-2-carboxylate is successfully decomposed using microwave irradiation to generate benzyne. This proof of concept investigation shows diphenyliodonium-2-carboxylate can be applied as an off-the-shelf benzyne precursor; by using microwave radiation, significantly reduced reaction times and lower b.p. solvents can facilitate a more universal application of this protocol than previously described. The investigation into the reactions of allylamino malonates with arynes is also described. Simple allylamino malonates are shown to perform a novel cascade aryne capture/ring-closure/[2,3]-rearrangement to generate indolin-3-one products. The influence of substitution of the indolin-3-one products on the photophysical properties is probed. Tetrahydropyridine derived aminomalonates result in a ring contraction by [2,3]-rearrangement to N-phenyl pyrrolidine products. Further investigations show N-allyl proline methyl esters also generate indolin-3-one products by this novel cascade mechanism. The photophysical properties of these products are also probed. N-diallylalanine methyl ester is shown to generate indolin-3-one with benzyne however N-allyl sarcosine ethyl ester generates the N-phenyl -allylated amino esters product by aryne capture/[2,3]-rearrangement