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1,3‐dipolar cycloaddition of diphenylnitrilimine to substituted dihydro‐3‐methylene‐2(3 H )‐furanones
Author(s) -
Štverková Slávka,
Žák Zdirad,
Jonas Jaroslav
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199519950365
Subject(s) - chemistry , methylene , furan , cycloaddition , bicyclic molecule , medicinal chemistry , formate , stereochemistry , organic chemistry , catalysis
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.