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Thermisch induzierte formale [3 + 2]‐Cycloadditionen von 3,3‐Dimethoxycyclopropen an Triazine, eine neue Synthese von Pyrrolo[1,2‐ d ][1,2,4]triazinen
Author(s) -
Rischke Monika,
Seitz Gunther,
Frenzen Gerlinde
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931261021
Subject(s) - chemistry , cycloaddition , dimethyl acetylenedicarboxylate , protonation , azirine , triazine , nitrone , bicyclic molecule , medicinal chemistry , crystal structure , stereochemistry , ring (chemistry) , polymer chemistry , crystallography , organic chemistry , ion , catalysis
Thermally Induced Formal [3 + 2] Cycloadditions of 3,3‐Dimethoxycyclopropene to Triazines, a Novel Synthesis of Pyrrolo[1,2‐ d ][1,2,4]triazines Formal [3 + 2] cycloaddition reactions of the π‐delocalized singlet vinylcarbene/three‐carbon 1,3‐dipole 8 , generated in a reversible, thermal ring opening of the cyclopropenone ketal 7 , with a variety of substituted triazines lead to the novel pyrrolo[1,2‐ d ][1,2,4]triazines 9 or 10 . Compound 10c is protonated at N‐2 by HClO 4 /HOAc to yield the salt 17c and alkylated at the same position by Meerwein reagent [O(CH 3 ) 3 BF 4 ] to give 18. 10c reacts smoothly with dimethyl acetylenedicarboxylate to provide the pyrido[2,1‐ f ]pyrrolo[1,2‐ d ][1,2,4]triazines 19 and 20 . The pyrrolotriazine 14 in the presence of oxygen, daylight, and silica gel is readily oxidized to the triazine N ‐oxide 22 . The crystal structures of 14 , of the protonated species 17c and of the N ‐oxide 22 have been determined by X‐ray diffraction methods.