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Reactions between Triazolinediones and Equilibrating Forms of Cycloheptatriene Derivatives Featuring 7,7‐Spiro and 1,7‐Fused Heterocyclic Rings
Author(s) -
Freccero Mauro,
Gandolfi Remo,
SarziAmade’ Mirko,
Bovio Bruna
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(20022)2002:3<569::aid-ejoc569>3.0.co;2-w
Subject(s) - chemistry , adduct , diastereomer , substituent , cycloheptatriene , moiety , nitrile , stereochemistry , diene , medicinal chemistry , organic chemistry , natural rubber
Nitrile oxide−azaheptafulvene adducts consist of rapidly equilibrating mixtures of fused ( 1 ) and spiro ( 2 ) isomers, the relative stabilities of which are nicely reproduced by B3LYP/6‐31G* calculations. The reaction between these compounds and MTAD affords only two diastereomeric adducts [ 9 (dominant) and 10 ], both deriving from the reaction of MTAD with 1 even in cases in which that isomer could not be detected by NMR spectroscopy. These adducts are formal Diels−Alder adducts deriving from attacks on the two diastereotopic faces of the triene moiety of 1 and involving only the diene system adjacent to the amino substituent (N 4 −C 4a =C 5 −C 6 =C 7 ). The structures of the adducts are firmly supported by spectroscopic data and X‐ray analysis, and so previous incorrect assignments are revised. The mechanism of the reaction between MTAD and 1 is briefly discussed.