Diels-Alder reactions of novel (1'-arylallylidene)cyclopropanes with heterodienophiles.
Palladium-catalyzed cross-coupling of various aryl iodides with bicyclopropylidene provided isolable (1'-arylallylidene)cyclopropanes, which reacted with a number of carbonyl compounds in the presence of Eu(fod)3 under high pressure to furnish oxaspiro[2.5]octene derivatives in moderate to good yields (22-69%). The reactions of the allylidenecyclopropanes with two azo compounds as dienophiles afforded diazaspiro[2.5]octenes in high yields (82 and 99%) even at ambient pressure. When treated with nitrosobenzene, two of the allylidenecyclopropanes gave the Diels-Alder adducts in up to 83 and 40% yield. 2,5-Diiodo-p-xylene coupled twice with bicyclopropylidene, and the product underwent a twofold Diels-Alder reaction with nitrosobenzene to produce the bis(spirocyclopropaneoxazine) derivative in 88% yield. This overall transformation can be brought about in a one-pot, two-step operation by addition of the nitrosoarene to the reaction mixture immediately after formation of the allylidenecyclopropanes to furnish various 5-oxa-4-azaspiro[2.5]oct-7-ene derivatives in 22-77% yield. The coupling of methyl bicyclopropylidenecarboxylate with 2,6-dimethylphenyl iodide produced a mixture of very stable regioisomeric allylidenecyclopropane derivatives in 90% yield. The reaction of this mixture with N-phenyltriazolinedione gave a corresponding mixture of the spirocyclopropanated heterobicycles in 61% yield.
Zhao
Ligang
L
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany.
Yucel
Baris
B
Scheurich
René Peter
RP
Frank
Daniel
D
de Meijere
Armin
A