The use of complex bases for the generation of arynes has been reviewed by Caubkre.' Diels-Alder reactions of benzyne with 1-vinylcyclobutene or with 1,2-dimethylenecyclobutane lead to tricyclic adducts (Scheme 1) which can be dehydrogenated with DDQ to give naphtho[a]cyclobutene or naphtho[b]cyclobutene, respectively. Similar reactions of 2,3-didehydronaphthalene with the dienes provide synthetic routes to anthrocyclobutenes.' Scheme 1 Arynic condensations have been used in several new syntheses of heterocyclic systems. Condensation of benzyne with diazocyclopentadienes gives 3H-indazole-(3-~piro)-cyclopentadienes.~ Treatment of N-phenyl 2-chlorobenzylamines or of N-phenyl 3-bromobenzylamines with potassium amide in liquid ammonia affords mixtures of dihydrophenanthridines and dihydrobenzazetes (Scheme 2).4 R 1 Ra/ \ Scheme 2
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