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Macrocyclization of α ‐(Alkynyloxy)silyl‐ α ‐diazoacetates by Inter‐/Intramolecular [3+2] Cycloaddition Reaction Sequences
Author(s) -
Maas Gerhard,
Gettwert Volker,
Krebs Fred,
Schmidtberg Günter
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/(sici)1521-3765(20000502)6:9<1646::aid-chem1646>3.0.co;2-c
Subject(s) - chemistry , cycloaddition , intramolecular force , diazo , silylation , stereochemistry , intermolecular force , crystallography , medicinal chemistry , molecule , catalysis , organic chemistry
Thermally induced intra‐/intermolecular [3+2] cycloaddition reaction sequences of α ‐(alkynyloxy)silyl‐ α ‐diazoacetates 1 lead to [3.3](1, 4/pyrazolophanes (2) 2 and higher cyclooligomers thereof [ (2) n , n >2]. In most cases, the cyclodimer was isolated by crystallization, while a complete separation of the mixture of the higher cyclooligomers was not possible. Solid state structures of cyclodimers (2 b) 2 and (2 c) 2 , cyclotrimer (2 b) 3 , and cyclotetramer (2 e) 4 were determined by X‐ray diffraction analysis. Field‐desorption mass spectra were used to characterize the cyclooligomer mixtures. The relative amounts of the cyclooligomers depend on the substitution pattern of the diazo compound. The cyclooligomerization reactions reported herein demonstrate, for the first time, the involvement of diazo functions in macrocyclization reactions via 1,3‐dipolar cycloaddition.