On the Reaction of 2-Pyrrolecarbaldehyde with Hetero-substituted Ethenes
3H-Pyrrolizines 1 have been obtained from reactions of 2-pyrrolecarbaldehyde with ethenylphosphonates 2 and the phosphane oxide 5, respectively, the ratio of products depending on the structure of the educts.On varying the reaction conditions a controlled synthesis of both isomers 1e/f was achieved.Pyrrolizines, formed in a reaction of 2-pyrrolecarbaldehyde with ethenyl phenyl sulfone (3), could not be isolated since the reaction proceeded to give more complex pyrrolizine derivatives and the cyclazine 11.A mechanism is proposed for this multistep reaction.N-Alkylatio n of 2-pyrrolecarbaldehyde with dihaloalkanes has been carried out using phase transfer catalysis.
Flitsch, Wilhelm,Lubisch, Wilfried
p. 1424 - 1435
(2007/10/02)
An Improved Synthesis of Cyclazines from 3H-Pyrrolizines
The reaction of 3H-pyrrolizines 3 with vinamidinium salts 4 provides a new and generally applicable route to cyclazines 5.Pyrrolizinefulvenes are intermediates of this reaction as shown using 3f as an example. - Cyclopentacyclazines 11 were prepared from the hitherto unknown 3H-pyrrolizines 3b, c, d and the pyrrolizine esters 3e, f with the cyclopentadiene iminium salt 10 under conditions which have been described previously.Additional evidence for a close similarity between cyclazines 11 and the corresponding azulenes has been obtained from the UV spectra of 11.
Batroff, Volker,Flitsch, Wilhelm,Leaver, Derek,Skinner, David
p. 1649 - 1658
(2007/10/02)
AN IMPROVED SYNTHESIS OF CYCLAZINES FROM 3H-PYRROLIZINES
Cyclazines are obtained in moderate yields by reaction of 3H-pyrrolizines bearing conjugative substituents (Ph or CO2Me) with vinamidinium salts in the presence of strong bases.Sytheses of the previously unknown 2-phenyl-3H-pyrrolizine and 1-methox