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Cycloadditions, 16. - Influence of Alkyl and Phenyl Groups in the Allenic ω-Position on the Intramolecular Diels-Alder Reactions of Allene Carbamides
Himbert, Gerhard,Diehl, Klaus,Schlindwein, Hans-Juergen
, p. 1691 - 1700 (2007/10/02)
The influences of methyl (partly of other alkyl) and phenyl moieties in the allenic ω-position on the isomerization tendencies of the N-phenyl- and N-(α-naphthyl)allenecarboxamides (5, 6 and 7, 8, resp.) are investigated.Methyl groups always decelerate (5, 7, 8 -> 9, 10, 11a-c), phenyl groups hinder (5f -> 9f and 12f), prevent (5, 6g), or accelerate (7f,g, 8g -> 10f,g, 11g) the intramolecular Diels-Alder reactions.The diphenyl compounds 5g, 6g cyclize to give the quinolones 12, 13; if this cyclization is prevented by two methyl groups in the ortho positions (s. 15), the common dimerization of allenes takes place to give the cyclobutane derivative 17. - Key Words: Allenecarboxamides/ Diels-Alder reaction/ Dimerization
