Premium
Zwitterions as Intermediates of the 1,3‐Dipolar Cycloaddition of Electrophilic Azides to 5‐Alkylidenedihydrotetrazoles – the Other Non‐Concerted Limiting Case
Author(s) -
Quast Helmut,
Regnat Dieter,
Peters EvaMaria,
Peters Karl,
von Schnering Hans Georg
Publication year - 1990
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199006951
Subject(s) - cycloaddition , steric effects , chemistry , electrophile , zwitterion , limiting , ring (chemistry) , computational chemistry , photochemistry , stereochemistry , medicinal chemistry , molecule , organic chemistry , catalysis , mechanical engineering , engineering
The isolable zwitterions 2 and the tetrahydrotetrazines 3 are formed in the 1,3 ‐dipolar cycloadditions of R 3 N 3 to 1 . It has been established X‐ray crystallo‐graphically that a strong steric hindrance is responsible for ring closure between the very close centers of opposite charge being difficult in 2 (R 1 = H, R 2 = t Bu = Mes). A detailed investigation of the reactions clearly confirms that the zwitterions 2 are actually the intermediates of a non‐concerted cycloaddition (R 1 = H. Me; R 2 = Me, t Bu; R 3 = (NO 2 ) 3 C 6 H 2 , p ‐Tos, Mes).