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The reactions of the ortho-quinones (5a-d) with the phosphorus ylide (6) afforded, besides the expected coumarin derivatives ( l o a d ) , compounds (9d), ( l l b and c), (13), and (14). When the reactions between compounds (5a-d) and (6) were carried out in the presence of ethyl vinyl ether (20) the pyran derivatives (21a, b, and d) and (22a, b, and d) were obtained as main products, by a [4 + 21 trapping process of the ortho-quinone methanide intermediates (7a, b, and d) with the dienophile (20). Similarly, the reaction between compounds (5a) and (6) in the presence of a-methylstyrene afforded mainly the pyrans (23 I and 11). Compounds (16), (19), and (24) were also prepared and studied.

Bis‐amidoxime 1 reacts with phosgene, thiophosgene and thionylchloride to give the corresponding bisfused oxadiazolo‐ and oxathiadiazoloquinoxalines 2, 4, 5 along with the unexpected furazano‐derivative 3, while monoamidoximes 9, 13 by treatment with ethyl chloroformate affords the oxadiazoloquinoxaline and the oxadiazolobenzothiazine derivatives 14, 15 along with the dicarboxylated product 16.

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