Alkylatlon orientation rules in conjugate addition of grignard reagents to nitropyrrole and nitrothiophene systems

R Ballini, G Bartoli, M Bosco, R Dalpozzo, E Marcantoni

Index: Ballini, Roberto; Bartoli, Giuseppe; Bosco, Marcella; Dalpozzo, Renato; Marcantoni, Enrico Tetrahedron, 1988 , vol. 44, # 20 p. 6435 - 6440

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Citation Number: 19

Abstract

Conjugate addition of various Grignard reagents to 1-alkyl-2-nitropyrroles and to 2- nitrothiophene has been investigated. 1-Alkyl-2-nitropyrroles undergo alkylation at 3 and 5 positions with prevalence of the latter isomer. On the contrary, in 2-nitrothiophene system, formation of the 3-isomer prevails. In both systems, a bulkier Grignard reagent favours the 5- isomer formation. This trend can be reversed increasing steric hindrance exerted by the 1- ...