Neighboring group effect of pyridazine and pyrazine rings for pi-facial selectivity in the reactions of fused isopropylidene-norbornene systems with electrophilic reagents

Citation
T. Kobayashi et al., Neighboring group effect of pyridazine and pyrazine rings for pi-facial selectivity in the reactions of fused isopropylidene-norbornene systems with electrophilic reagents, J CHEM S P1, (12), 2001, pp. 1372-1385
Citations number
46
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1
ISSN journal
1472-7781 → ACNP
Issue
12
Year of publication
2001
Pages
1372 - 1385
Database
ISI
SICI code
1472-7781(2001):12<1372:NGEOPA>2.0.ZU;2-R
Abstract
A series of pyridazine- and pyrazine-fused isopropylidenenorbornenes(dagger ) have been synthesized and the-facial selectivity of the electrophilic rea ctions with 4-phenyl-1,2,4-triazole-3,5(4H)-dione (PTAD), m-chloroperbenzoi c acid (MCPBA) and N-bromosuccinimide (NBS) has been investigated. The ene reactions with PTAD exhibited exclusive syn selectivity to the heteroaromat ic rings except for an isopropylidenenorbornene fused with a pyridazine N-o xide ring. The epoxidations with MCPBA and the ene reactions with NBS affor ded mixtures of syn and anti isomers depending on the heteroaromatic rings and substituents. The predominant syn selectivity compared with that of a b enzene-fused congener may be attributed to the presence of a strong positiv e electrostatic potential field over the heteroaromatic ring to stabilize a polar transition state by the electrostatic interaction.