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1,3-dipolar cycloaddition of diphenylnitrilimine to substituted dihydro-3-methylene-2(3H)-furanones

✍ Scribed by Štverková, Slávka ;Žák, Zdirad ;Jonas, Jaroslav

Publisher
John Wiley and Sons
Year
1995
Tongue
English
Weight
397 KB
Volume
1995
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

Substituted 4,5‐dihydro‐3‐methylene‐2(3__H__)‐furanones 1 react as dipolarophiles with diphenylnitrilimine to give the corresponding spiro[furan‐pyrazolin]ones 2. From the compound 1a, 1,3‐diphenyl‐7‐oxa‐1,2‐diazaspiro[4,4]non‐2‐en‐6‐one (2a) is formed. In the other cases, a primarily formed cycloadduct undergoes rearrangement during the reaction to the bicyclic compound 5. Thus, addition of diphenylnitrilimine to (E)‐1b, (Z)‐1b and (E)‐1c leads to compound 5b, whereas reactions of (E)‐ or (Z)‐1f and (E)‐1g give the corresponding compound 5f and 5g, respectively. The structure of 5b was determined by X‐ray analysis. Labeled methyl formate (H^13^CO~2~CH~3~) was used for labeling the methylene carbon atom in 4,5‐dihydro‐3‐(p‐tosyloxymethylene)‐2(3H)‐furanone [(E)‐1b] in order to ascertain the structure of the intermediate cycloadduct as well as the pathway of the consecutive rearrangement.

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