Annellated arynes

A different type of geometrical effect has been noted in bicyclic arynes. As the annelated ring is decreased in size from six- to four-membered the ease of formation of the arynes 669, 670, and 671 increases in that order. Regardless of whether this observation is due to differences in the stability of the arynes themselves or of some kinetically important intermediates leading to the arynes, " its ultimate cause is probably related to bond fixation brought about by the geometric constraints of the annelated ring. 

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