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Intramolekulare 1,3‐dipolare Cycloadditionen mit alkenyl‐substituierten 3,4‐Diarylsydnonen
Author(s) -
Meier Hansruedi,
Heimgartner Heinz
Publication year - 1986
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19860690421
Subject(s) - chemistry , intramolecular force , cycloaddition , substituent , nitrile , decarboxylation , medicinal chemistry , yield (engineering) , imine , stereochemistry , intramolecular reaction , 1,3 dipolar cycloaddition , photochemistry , organic chemistry , catalysis , metallurgy , materials science
Intramolecular 1,3‐Dipolar Cycloaddition Reactions of Alkenyl‐substituted 3,4‐Diarylsydnones The 3,4‐diarylsydnones 1 and 12a–e with an allyl or alkenyloxy substituent on the N(3)‐phenyl group have been synthesized by classical methods starting from 2‐allylaniline and the corresponding alkenyloxyanilines, respectively ( Schemes 2 and 3 ). Whereas the allyl‐substituted sydnone 1 undergoes an intramolecular 1,3‐dipolar cycloaddition at room temperature in solution to yield 13 ( Scheme 4 ), the alkenyloxy‐substituted sydnones 12a–e are thermally stable. On irradiation of 1 and 12a–d , formation of the fused dihydropyrazoles 2 and 14a–d ( Schemes 1 and 5 ) is observed. In the case of 12d , the yield of 14d is very low, and the symmetric 1,2,3‐triazole 15a has been isolated as the main product. A very likely reaction mechanism for the formation of the photoproducts involves decarboxylation of the sydnones to give a nitrile‐imine which undergoes an intramolecular 1,3‐dipolar cycloaddition onto the CC bond.